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BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA
HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH
Checklist: Database Connection Issues
Markus Flechtner
Trivadis – Our mission.
Checklist: Database Connection Issues
2 17.05.2022
Trivadis makes IT easier:
We provide significant support for our
customers in the smart use of data in
the digital age.
We reduce complexity for our
customers through outstanding
technological expertise.
We take over key tasks in the existing
and future IT of our customers.
Trivadis – What sets us apart.
Checklist: Database Connection Issues
3 17.05.2022
We understand the business processes and economic challenges of our customers and
support them through IT consulting and in the development of comprehensive IT solutions.
Our proven products, developed by Trivadis, are based on in-depth expertise in the key
technologies offered by Microsoft, Oracle and Open Source.
That sets us apart from the competition.
A selection of awards we have received
OPEN SOURCE
Trivadis – Our key figures
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4 17.05.2022
Founded in 1994
15 Trivadis locations with
more than 650 employees
Sales of CHF 111 million (EUR 96
million)
Over 250 Service Level Agreements
More than 4000 training participants
Research and development budget: CHF
5.0 million
More than 1900 projects each year with
over 800 customers
Financially independent and sustainably
profitable
About me .. Markus Flechtner
Principal Consultant, Trivadis, Duesseldorf/Germany, since April 2008
Working with Oracle since the 1990’s
– Development (Forms, Reports, PL/SQL)
– Support
– Database Administration
Focus
– Oracle Real Application Clusters
– Database Upgrade and Migration Projects
Teacher
– O-RAC – Oracle Real Application Clusters
– O-NF-DBA – Oracle Database New Features for the DBA
– O-MT – Oracle Multitenant
– PG4ORA – PostgreSQL for Oracle DBAs
Blog:
https://markusdba.net/
@markusdba
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6
Technology on its own won't help you.
You need to know how to use it properly.
Agenda
Checklist: Database Connection Issues
7 17.05.2022
1. The trivial part: are the database and the listener running?
2. Check Network Infrastructure
3. Oracle Net Configuration
4. Try an Oracle Net Connection using Instant Client
5. Check Oracle Client Version
6. Check Password Versions
7. Oracle Net Logging & Tracing
8. Miscellaneous
9. More information
Before you start ..
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8 17.05.2022
Has it ever worked before?
If yes, what was changed?
– "I changed nothing, I only improved some things .." 
Is the issue specific to a single client or a small set of clients?
– Local configuration issue?
– Same network segment => routing issue?
Are all clients affected?
– Server configuration issue?
– No routing to server?
– Central switch/firewall configuration?
Checklist: Database Connection Issues
9 17.05.2022
The trivial part
Check Database and Listener?
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10 17.05.2022
Is the database instance running?
Is the (correct) listener running?
– Especially important when you have got multiple listeners running
– When a listener serves multiple database versions: listener should run with the highest
database version
Is the database instance registered with the (correct) listener?
– If LOCAL_LISTENER is not set => instance registers with listener on port 1521
Listener Status – lsnrctl status
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oracle@training19c:~/ [TVDNCDB] lsnrctl status
[…] Alias LISTENER
Version TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date 11-MAY-2019 11:01:30
Uptime 0 days 0 hr. 15 min. 47 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u00/app/oracle/network/admin/listener.ora
Listener Log File /u00/app/oracle/diag/tnslsnr/training19c/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=training19c.trivadistraining.com)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=training19c.trivadistraining.com)(PORT=5500))(Security=(my_w
allet_directory=/u00/app/oracle/admin/TVDNCDB/xdb_wallet))(Presentation=HTTP)(Session=RAW))
Services Summary...
Service "TVDNCDB.trivadistraining.com" has 1 instance(s).
Instance "TVDNCDB", status READY, has 1 handler(s) for this service...
Service "TVDNCDBXDB.trivadistraining.com" has 1 instance(s).
Instance "TVDNCDB", status READY, has 1 handler(s) for this service...
The command completed successfully
Listener-logging should be
enabled when diagnosing
connection issues
Host+Port
Registered Services
Is the listener using the
correct listener.ora file?
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Check Network Infrastructure
Check Network Infrastructure (1)
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Check firewalls on client and server
Check network connectivity between client and server
– Ping (please note that ping uses the ICMP/IP protocol (not the TCP protocol)
– telnet from client to server on the Oracle Net port (if telnet is installed)
Name resolution from client to server
– Nslookup
– /etc/hosts
Do not forget to involve the system administrator and the network administrators
Check Network Infrastructure (2)
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Check for errors on network interface level
oracle@training19c:~/ [rdbms19000] ifconfig enp0s3
enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.56.108 netmask 255.255.255.0 broadcast 192.168.56.255
inet6 fe80::3da9:2515:3ce2:2115 prefixlen 64 scopeid 0x20<link>
ether 08:00:27:b9:d8:65 txqueuelen 1000 (Ethernet)
RX packets 1962 bytes 169328 (165.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1148 bytes 235620 (230.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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Oracle Net Configuration
Oracle Net Configuration (1) – Listener does not start
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The listener does not start or uses the wrong port or hostname
– Check if the correct listener.ora is used
– Check value of $TNS_ADMIN
– Look for other listener.ora files on the database server, try to consolidate
– Multiple entries for the same listener in the listener.ora file?
Error "TNS-00512: Address already in use"
– Reason: Duplicate use of a TCP-Port
Error "NL-00303: syntax error in NV string"
– Syntax error in the listener.ora file
– In most cases "bracket errors"
Oracle Net Configuration (2) – Domain Name issues
Checklist: Database Connection Issues
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Oracle Net and Oracle Database can be configured using domains
Two areas:
– Instance parameter DB_DOMAIN => determines domain part of the default service name
which is registered with the listener
– Sqlnet.ora parameter NAMES.DEFAULT_DOMAIN => defines default domain for Oracle Net
connections
Inconsistencies can lead to " TNS-03505: Failed to resolve name"
Recommendations:
– Use consistent naming (DB_DOMAIN = NAMES.DEFAULT_DOMAIN)
– Use full qualified alias names in tnsnames.ora
– Use full qualified alias names on your clients (connection descriptors, JDBC URL etc.)
Oracle Net Configuration (3) – tnsping
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Tnsping helps you to find out
– Can the alias name be resolved?
– Which source is used for name resolution (LDAP, local tnsnames)?
– To which connection data is the alias resolved?
– Is there a listener running which is listening on the given hostname and port?
Tnsping does not check if there is a database instance running which provides the service
specified in the connection string
– You have to use e.g. SQL*Plus (or another tool which connects to the database) to
check this
Oracle Net Configuration (4) – tnsping
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Sucessful tnsping:
oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019 13:24:36
Copyright (c) 1997, 2019, Oracle. All rights reserved.
Used parameter files:
/u00/app/oracle/network/admin/sqlnet.ora
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST =
training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED)
(SERVICE_NAME = PDB01.trivadistraining.com)))
OK (0 msec)
Location of the Oracle Net configuration files which are used
Naming method which is used (local tnsnames.ora)
Allowed methods and priorities are defined in sqlnet.ora
(NAMES.DIRECTORY_PATH)
Success
Oracle Net Configuration (5) – tnsping
Checklist: Database Connection Issues
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Name can be resolved, but no listener is running on given port and host:
Name cannot be resolved
oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01
[..]
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST =
training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED)
(SERVICE_NAME = PDB01.trivadistraining.com)))
TNS-12541: TNS:no listener Check if host and port are correct
oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01A
[..]
Used parameter files:
/u00/app/oracle/network/admin/sqlnet.ora
TNS-03505: Failed to resolve name
Check tnsnames.ora if entry exists
Oracle Net Configuration (6) – Database Connection
Checklist: Database Connection Issues
21 17.05.2022
Use SQL*Plus to check if the given database service is available:
oracle@training19c:/u00/app/oracle/network/trc/ [TVDNCDB] tnsping TVDNCDB
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019 15:08:23
[..]
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST =
training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED)
(SERVICE_NAME = TVDNCDB.trivadistraining.com)))
OK (0 msec)
oracle@training19c:/u00/app/oracle/network/trc/ [rdbms19000] sqlplus
system/manager@TVDNCDB
SQL*Plus: Release 19.0.0.0.0 - Production on Sat May 11 15:05:43 2019
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor
Listener is up, but there is no instance
registered which provides the service
Oracle Net Configuration (7) – Service Registration
Checklist: Database Connection Issues
22 17.05.2022
When a database instance is started, it registers itself with the listener (PMON process
(before 12c) or LREG process)
– Parameter LOCAL_LISTENER
As soon as the registration is complete, the listener is aware of the services which are
provided by the database instance
If you bounce the listener while the database is running, it can take up to 60 seconds
before the database "renews" the registration.
– This may lead to a (temporary) ORA-12514:
– You can enforce the registration:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor
SQL> alter system register;
System altered.
Oracle Net Configuration (8) – Easy Connect
Checklist: Database Connection Issues
23 17.05.2022
If you want to rule out name resolution via LDAP or tnsnames, you can try Easy Connect
1. Allow Easy Connect via sqlnet.ora
2. Test the connection with Easy Connect (Host:Port/Service)
NAMES.DIRECTORY_PATH=(LDAP, TNSNAMES, EZCONNECT )
oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping
training19c.trivadistraining.com:1521/PDB01.trivadistraining.com
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019
13:56:58
Copyright (c) 1997, 2019, Oracle. All rights reserved.
Used parameter files:
/u00/app/oracle/network/admin/sqlnet.ora
Used EZCONNECT adapter to resolve the alias
Attempting to contact
(DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=PDB01.trivadistraining.com))(ADDRESS=
(PROTOCOL=tcp)(HOST=192.168.56.108)(PORT=1521)))
OK (0 msec)
Oracle Net Configuration (9) – Timeout
Checklist: Database Connection Issues
24 17.05.2022
With slow network connections, it can be helpful to check (and change) the timeout
parameters
sqlnet.ora
Use "0" to disable a parameter
Check your OS specific documentation for changing timeouts on OS level
SQLNET.INBOUND_CONNECT_TIMEOUT=n # server only, default 60 seconds,
# time allowed for authentication
SQLNET.OUTBOUND_CONNECT_TIMEOUT=n
SQLNET.RECV_TIMEOUT=n
SQLNET.SEND_TIMEOUT=n
TCP.CONNECT_TIMEOUT=n # default 60 seconds, time allowed to
# establish a TCP connection
Oracle Net Configuration (10) – tnsnames.ora in
general
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Recommendations
– All entries should be full qualified (especially when using a names.default_domain)
– Check for duplicate entries
– Check for "bracket errors"
– Errors in one entry may lead to name resolution failures in subsequent entries
==> add new entries at the end of the tnsnames.ora file
Example entry
PDB01.TRIVADISTRAINING.COM =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = training19c.trivadistraining.com)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = PDB01.trivadistraining.com)
) )
All names full qualified!
Checklist: Database Connection Issues
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Check Connectivity with the
Oracle Instant Client
Oracle Instant Client
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Lightweight Oracle Client
Requires no administrator or root privileges during installation
– Just unzip
Modular configuration, e.g. modules
– Required: "Basic Package " or "Basic Light Package"
– SQL*Plus Package
– JDBC Package
– ODBC Package
Download:
https://www.oracle.com/technetwork/database/database-technologies/instant-
client/downloads/index.html
Connection Tests using Instant Client
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In order to rule out configuration issues with your application, you can use instant client for
testing connections
– E.g. from your database server to your database server (using Oracle Net)
– From your application server to the database server
– Etc.
Procedure
1. Download and unzip all required packages
2. Set environment variables
3. Use your own Oracle Net configuration (tnsnames.ora etc.) for testing (=> set TNS_ADMIN)
4. Test the connection
Checklist: Database Connection Issues
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Check Oracle Client Version
Oracle Client – Server Certification (1)
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30 17.05.2022
* 11.2.0.3 or 11.2.0.4 only
** was a supported combination, but is currently out of support
Special = limited support (special contract required)
Source: MOS note 207303.1
Client
Server
19c/18c/12.2 12.1 11.2 (*) 11.1 10.2
19c/18c /12.2 OK OK OK NO NO
12.1 OK OK OK NO** Special
11.2 (*) OK* OK OK NO** Special
11.1 NO NO** NO** NO** NO**
10.2 NO Special Special NO** Special
Oracle Client – Server Certification (2)
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31 17.05.2022
Older clients may be able to connect, but there may be limited functionality or "strange
error messages" may occur
The minimum client version which can be used to connect to an Oracle 12.2 database (or
later) is Oracle 8i (8.1)
Especially when using Oracle Net encryption (free with every edition of the database)
older clients may no be able to connect
This may lead to connection issues after upgrading a database!
–  Check the client versions before upgrading a database!
Oracle Client – Find out the client versions
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select
sc.client_version,sc.client_driver,
s.machine,s.program,s.osuser,s.service_name,count(*)
from gv$session s,gv$session_connect_info sc
where sc.inst_id=s.inst_id
and sc.sid=s.sid and sc.serial#=s.serial#
and s.type<>'BACKGROUND'
group by sc.client_version,sc.client_driver,s.machine,s.program,s.osuser,s.service_name
order by sc.client_version,sc.client_driver,s.machine,s.program,s.osuser,s.service_name
/
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Check Password Versions
Check Password Versions
Checklist: Database Connection Issues
34 17.05.2022
Case-Sensitive Passwords
– Introduced with Oracle 10g
– Parameter SEC_CASE_SENSITIVE_LOGON as a workaround
– Parameter deprecated since Oracle 12c
Using SEC_CASE_SENSITIVE_LOGON will result in an ORA-32004 when starting the
database instance
– Solution: remove the parameter from the spfile
ORA-32004: obsolete or deprecated parameter(s) specified for %s instance
SQL> ALTER SYSTEM RESET sec_case_sensitive_logon scope=spfile sid='*';
Password versions (1)
Checklist: Database Connection Issues
35 17.05.2022
The algorithm for the password hashes was changed since Oracle 10c
– There may be different password versions (= password hashes) stored in the database
– A client needs a "compatible" password version in order to connect
SQL select password_versions from dba_users;
PASSWORD_VERSIONS
-----------------
10G 11G 12C
11G 12C
[..]
Password versions (2) – the problem
Checklist: Database Connection Issues
36 17.05.2022
The parameter SQLNET.ALLOWED_LOGON_VERSION_SERVER determines, which
password hashes are generated
– Default in Oracle 12.2: 12
–  Only 11G + 12C Hashes will be generated
–  10g-Clients cannot connect
ORA-1017: invalid username/password; logon denied
Password versions (3) – the solution
Checklist: Database Connection Issues
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1. Set SQLNET.ALLOWED_LOGON_VERSION_SERVER = 8
-  all password hashes will be generated
2. Make the database generate new password hashes (for users which are used by
Oracle 10g clients)
3. Users with Oracle 10g clients can connect 
SQL> ALTER USER <user> identified by <EXISTING_PASSWORD>;
Checklist: Database Connection Issues
38 17.05.2022
Oracle Net Logging & Tracing
Introduction
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39 17.05.2022
Logging and tracing can provide more detailled information in order to diagnose
connectivity issues
Can be enabled on
– Listener Level
– Client Level
– Server Level
Tracing and logging can generate a huge number of large files,
do not forget to disable it after the issue has been solved
Listener.log (1)
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Enable listener logging
Listener.ora
Location of the listener.log in ADR:
Check the listener.log after each (failed) connection attempt for any error message
Listener.log can become huge => resize it before testing, e.g.
cp listener.log listener.log.backup; echo "" >listener.log
# enable or disable listener.log
LOGGING_LISTENER = ON
# Logging parameters, ignored if ADR is used
#LOG_DIRECTORY_LISTENER = /u00/app/oracle/network/log
#LOG_FILE_LISTENER = listener.log
$ORACLE_BASE/diag/tnslsnr/<hostname>/<listener_name>/trace
Listener.log (2) - Example
Checklist: Database Connection Issues
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11-DEC-2014 08:10:14 * (CONNECT_DATA=(CID=(PROGRAM=SQL
Developer)(HOST=__jdbc__)(USER=mbg))(SERVER=DEDICATED)(SERVICE_NAME=TVD12.
trivadistraining.com)) *
(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.1)(PORT=54163)) * establish *
TVD12.trivadistraining.com * 0
11-DEC-2014 08:10:59 *
(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=TVD12.trivadistraining.com)(
CID=(PROGRAM=C:Program?FilesDellToad?for?Oracle?12.6?TrialToad.exe)(HO
ST=LTMBG02)(USER=mbg))) *
(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.1)(PORT=54182)) * establish *
TVD12.trivadistraining.com * 0
Listener Tracing
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The listener uses the ADR infrastructure by default
For the classical version, the ADR must be deactivated in the LISTENER.ORA and the
listener must be restarted (DIAG_ADR_ENABLED_LISTENER=OFF)
Different trace levels are possible:
– OFF (0), USER (4), ADMIN (8), or SUPPORT (16)
DIAG_ADR_ENABLED_LISTENER = OFF
TRACE_LEVEL_LISTENER = 16
TRACE_DIRECTORY_LISTENER = /u00/app/oracle/network/trc
TRACE_FILE_LISTENER = listener.trc
TRACE_TIMESTAMP_LISTENER = TRUE
Server Logging
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43 17.05.2022
Logging parameters
LOG_DIRECTORY_SERVER = /u00/app/oracle/network/log
LOG_FILE_SERVER = sqlnet_server.log
Server Tracing
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44 17.05.2022
Since Oracle 11g trace and log files are stored by the client and the server in the
Automatic Diagnostic Directory (ADR)
For the classical version, the ADR must be deactivated in the SQLNET.ORA
Different trace levels are possible:
– OFF (0), USER (4), ADMIN (8), or SUPPORT (16)
The TRACE_*_SERVER parameters can then be set
TRACE_LEVEL_SERVER = 16
TRACE_DIRECTORY_SERVER = /u00/app/oracle/network/trc
TRACE_FILE_SERVER = sqlnet_server.trc
TRACE_TIMESTAMP_SERVER = TRUE
DIAG_ADR_ENABLED = OFF
Client Logging
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45 17.05.2022
Logging Parameters
Example:
LOG_DIRECTORY_CLIENT = /u00/app/oracle/network/log
LOG_FILE_CLIENT = sqlnet_client.log
oracle@training19c:/u00/app/oracle/network/log/ [TVDNCDB] cat sqlnet_client.log
***********************************************************************
Fatal NI connect error 12514, connecting to:
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=training19c.trivadistraining.com)(PORT=1521))(CONNECT_D
ATA=(SERVER=DEDICATED)(SERVICE_NAME=TVDNCDB.trivadistraining.com)(CID=(PROGRAM=sqlplus)(HOST=trai
ning19c.trivadistraining.com)(USER=oracle))))
VERSION INFORMATION:
TNS for Linux: Version 19.0.0.0.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 19.0.0.0.0 - Production
Version 19.3.0.0.0
Time: 11-MAY-2019 15:05:43
Tracing to file: /u00/app/oracle/network/trc/sqlnet_client_19495.trc
Tns error struct:
ns main err code: 12564
[..]
Client Tracing
Checklist: Database Connection Issues
46 17.05.2022
For the classical version, the ADR must be deactivated in the SQLNET.ORA
Different trace levels are possible:
– OFF (0), USER (4), ADMIN (8), or SUPPORT (16)
The TRACE_*_SERVER parameters can then be set
DIAG_ADR_ENABLED = OFF
TRACE_LEVEL_CLIENT = 16
TRACE_DIRECTORY_CLIENT = /u00/app/oracle/network/trc
TRACE_FILE_CLIENT = sqlnet_client.trc
TRACE_TIMESTAMP_CLIENT = TRUE
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47 17.05.2022
Miscellaneous
Increase the Array Fetch Size
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48 17.05.2022
Not in order to solve connection issues, but to improve performance
Increasing the array size will
– Reduce the number of fetches
– Reduce the number of packets to be transferred
Default value is 15
Changing the array fetch size is not always an option (think of 3rd party software)
SQLPLUS> SET ARRAYSIZE 49
Network Performance - Packet Size – MTU & SDU
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Both are performance related settings
MTU (Maximum Transmission Unit)
– Default: 1460 bytes
– Enlarging this value can help to reduce the number of packets sent over the network
– All network components must support higher values and have to be changed accordingly
SDU (Session data unit)
– Changing the "Session data unit" size can help to reduce Oracle Net related wait events
('SQL*Net message to client' and 'SQL*Net more data to client')
– Setting the default SDU size on client and server in sqlnet.ora
– Or use "(SDU_SIZE=8192)" in listener.ora and tnsnames.ora
DEFAULT_SDU_SIZE=8192
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More information
MOS-Notes (1)
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51 17.05.2022
Oracle Net Diagnostics (Doc ID 834822.1)
SQL*Net & Oracle Net Services - Tracing and Logging at a Glance (Doc ID 219968.1)
How to Enable Oracle SQL*Net Client , Server , Listener , Kerberos and External procedure
Tracing from Net Manager (Doc ID 395525.1)
How To Limit Connections Generating Trace when Oracle Net Server Enabled (Doc ID 401134.1)
Intended Usage of the TNSPING Utility (Doc ID 787848.1)
How to Match Oracle Net Client and Server Trace Files (Doc ID 374116.1)
How to Perform the Equivalent of SQL*Net Client Tracing with Oracle JDBC Thin Driver (Doc ID
793415.1)
Shared Server (MTS) Diagnostics (Doc ID 1005259.6)
How to Diagnose Slow TNS Listener / Connection Performance (Doc ID 557416.1)
Listener Hanging - Information to Get For Resolving or Troubleshooting (Doc ID 230156.1)
Oracle Net (SQL*Net) Timeout Parameters (Doc ID 1560775.1)
MOS-Notes (2)
Checklist: Database Connection Issues
52 17.05.2022
Oracle Net Diagnostic Examples (Doc ID 1384945.1)
How to Reduce the TCP/IP Timeout for Oracle Net on Solaris (Doc ID 275189.1)
How to Configure Linux OS Ethernet TCP/IP Networking (Doc ID 132044.1)
Change MTU Size in Oracle Linux (Doc ID 2520148.1)
The relation between MTU (Maximum Transmission Unit) and SDU (Session Data Unit) (Doc ID
274483.1)
SQL*Net Packet Sizes (SDU & TDU Parameters) (Doc ID 44694.1)
Troubleshooting Waits for 'SQL*Net message to client' and 'SQL*Net more data to client' Events
from a Performance Perspective (Doc ID 1404526.1)
Oracle Net Performance Tuning (Doc ID 67983.1)
Starting With Oracle JDBC Drivers - Installation, Certification, and More! (Doc ID 401934.1)
SQL*Net & Oracle Net Services - Tracing and Logging at a Glance (Doc ID 219968.1)
RAC/SCAN: How to set SDU, Queuesize and Other Net Parameters for RAC Listeners (Doc ID
1292915.1)
Oracle Documentation & Other Links
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Documentation
– Net Services Administator's Guide - Part III Testing and Troubleshooting Oracle Net Services
https://docs.oracle.com/en/database/oracle/oracle-database/19/netag/part-III-test-and-
troubleshoot-oracle-net-services.html#GUID-E8B29E61-3236-486B-AB89-665215E86CFA
Other Links
– http://www.oracledbaplusbigdata.com/2018/01/27/sqlnet-ora-logging-and-tracing/
Questions and Answers
Markus Flechtner
Principal Consultant
Phone +49 211 5866 64725
Markus.Flechtner@Trivadis.com
@markusdba http://markusdba.de
Download the slides from https://www.slideshare.net/markusflechtner
Please don‘t forget the session evaluation – Thank you!
17.05.2022 Checklist: Database Connection Issues
54

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Oracle Database: Checklist Connection Issues

  • 1. BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH Checklist: Database Connection Issues Markus Flechtner
  • 2. Trivadis – Our mission. Checklist: Database Connection Issues 2 17.05.2022 Trivadis makes IT easier: We provide significant support for our customers in the smart use of data in the digital age. We reduce complexity for our customers through outstanding technological expertise. We take over key tasks in the existing and future IT of our customers.
  • 3. Trivadis – What sets us apart. Checklist: Database Connection Issues 3 17.05.2022 We understand the business processes and economic challenges of our customers and support them through IT consulting and in the development of comprehensive IT solutions. Our proven products, developed by Trivadis, are based on in-depth expertise in the key technologies offered by Microsoft, Oracle and Open Source. That sets us apart from the competition. A selection of awards we have received OPEN SOURCE
  • 4. Trivadis – Our key figures Checklist: Database Connection Issues 4 17.05.2022 Founded in 1994 15 Trivadis locations with more than 650 employees Sales of CHF 111 million (EUR 96 million) Over 250 Service Level Agreements More than 4000 training participants Research and development budget: CHF 5.0 million More than 1900 projects each year with over 800 customers Financially independent and sustainably profitable
  • 5. About me .. Markus Flechtner Principal Consultant, Trivadis, Duesseldorf/Germany, since April 2008 Working with Oracle since the 1990’s – Development (Forms, Reports, PL/SQL) – Support – Database Administration Focus – Oracle Real Application Clusters – Database Upgrade and Migration Projects Teacher – O-RAC – Oracle Real Application Clusters – O-NF-DBA – Oracle Database New Features for the DBA – O-MT – Oracle Multitenant – PG4ORA – PostgreSQL for Oracle DBAs Blog: https://markusdba.net/ @markusdba 17.05.2022 Checklist: Database Connection Issues 5
  • 6. 17.05.2022 Checklist: Database Connection Issues 6 Technology on its own won't help you. You need to know how to use it properly.
  • 7. Agenda Checklist: Database Connection Issues 7 17.05.2022 1. The trivial part: are the database and the listener running? 2. Check Network Infrastructure 3. Oracle Net Configuration 4. Try an Oracle Net Connection using Instant Client 5. Check Oracle Client Version 6. Check Password Versions 7. Oracle Net Logging & Tracing 8. Miscellaneous 9. More information
  • 8. Before you start .. Checklist: Database Connection Issues 8 17.05.2022 Has it ever worked before? If yes, what was changed? – "I changed nothing, I only improved some things .."  Is the issue specific to a single client or a small set of clients? – Local configuration issue? – Same network segment => routing issue? Are all clients affected? – Server configuration issue? – No routing to server? – Central switch/firewall configuration?
  • 9. Checklist: Database Connection Issues 9 17.05.2022 The trivial part
  • 10. Check Database and Listener? Checklist: Database Connection Issues 10 17.05.2022 Is the database instance running? Is the (correct) listener running? – Especially important when you have got multiple listeners running – When a listener serves multiple database versions: listener should run with the highest database version Is the database instance registered with the (correct) listener? – If LOCAL_LISTENER is not set => instance registers with listener on port 1521
  • 11. Listener Status – lsnrctl status Checklist: Database Connection Issues 11 17.05.2022 oracle@training19c:~/ [TVDNCDB] lsnrctl status […] Alias LISTENER Version TNSLSNR for Linux: Version 19.0.0.0.0 - Production Start Date 11-MAY-2019 11:01:30 Uptime 0 days 0 hr. 15 min. 47 sec Trace Level off Security ON: Local OS Authentication SNMP OFF Listener Parameter File /u00/app/oracle/network/admin/listener.ora Listener Log File /u00/app/oracle/diag/tnslsnr/training19c/listener/alert/log.xml Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER))) (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=training19c.trivadistraining.com)(PORT=1521))) (DESCRIPTION=(ADDRESS=(PROTOCOL=tcps)(HOST=training19c.trivadistraining.com)(PORT=5500))(Security=(my_w allet_directory=/u00/app/oracle/admin/TVDNCDB/xdb_wallet))(Presentation=HTTP)(Session=RAW)) Services Summary... Service "TVDNCDB.trivadistraining.com" has 1 instance(s). Instance "TVDNCDB", status READY, has 1 handler(s) for this service... Service "TVDNCDBXDB.trivadistraining.com" has 1 instance(s). Instance "TVDNCDB", status READY, has 1 handler(s) for this service... The command completed successfully Listener-logging should be enabled when diagnosing connection issues Host+Port Registered Services Is the listener using the correct listener.ora file?
  • 12. Checklist: Database Connection Issues 12 17.05.2022 Check Network Infrastructure
  • 13. Check Network Infrastructure (1) Checklist: Database Connection Issues 13 17.05.2022 Check firewalls on client and server Check network connectivity between client and server – Ping (please note that ping uses the ICMP/IP protocol (not the TCP protocol) – telnet from client to server on the Oracle Net port (if telnet is installed) Name resolution from client to server – Nslookup – /etc/hosts Do not forget to involve the system administrator and the network administrators
  • 14. Check Network Infrastructure (2) Checklist: Database Connection Issues 14 17.05.2022 Check for errors on network interface level oracle@training19c:~/ [rdbms19000] ifconfig enp0s3 enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.56.108 netmask 255.255.255.0 broadcast 192.168.56.255 inet6 fe80::3da9:2515:3ce2:2115 prefixlen 64 scopeid 0x20<link> ether 08:00:27:b9:d8:65 txqueuelen 1000 (Ethernet) RX packets 1962 bytes 169328 (165.3 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 1148 bytes 235620 (230.0 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
  • 15. Checklist: Database Connection Issues 15 17.05.2022 Oracle Net Configuration
  • 16. Oracle Net Configuration (1) – Listener does not start Checklist: Database Connection Issues 16 17.05.2022 The listener does not start or uses the wrong port or hostname – Check if the correct listener.ora is used – Check value of $TNS_ADMIN – Look for other listener.ora files on the database server, try to consolidate – Multiple entries for the same listener in the listener.ora file? Error "TNS-00512: Address already in use" – Reason: Duplicate use of a TCP-Port Error "NL-00303: syntax error in NV string" – Syntax error in the listener.ora file – In most cases "bracket errors"
  • 17. Oracle Net Configuration (2) – Domain Name issues Checklist: Database Connection Issues 17 17.05.2022 Oracle Net and Oracle Database can be configured using domains Two areas: – Instance parameter DB_DOMAIN => determines domain part of the default service name which is registered with the listener – Sqlnet.ora parameter NAMES.DEFAULT_DOMAIN => defines default domain for Oracle Net connections Inconsistencies can lead to " TNS-03505: Failed to resolve name" Recommendations: – Use consistent naming (DB_DOMAIN = NAMES.DEFAULT_DOMAIN) – Use full qualified alias names in tnsnames.ora – Use full qualified alias names on your clients (connection descriptors, JDBC URL etc.)
  • 18. Oracle Net Configuration (3) – tnsping Checklist: Database Connection Issues 18 17.05.2022 Tnsping helps you to find out – Can the alias name be resolved? – Which source is used for name resolution (LDAP, local tnsnames)? – To which connection data is the alias resolved? – Is there a listener running which is listening on the given hostname and port? Tnsping does not check if there is a database instance running which provides the service specified in the connection string – You have to use e.g. SQL*Plus (or another tool which connects to the database) to check this
  • 19. Oracle Net Configuration (4) – tnsping Checklist: Database Connection Issues 19 17.05.2022 Sucessful tnsping: oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01 TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019 13:24:36 Copyright (c) 1997, 2019, Oracle. All rights reserved. Used parameter files: /u00/app/oracle/network/admin/sqlnet.ora Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = PDB01.trivadistraining.com))) OK (0 msec) Location of the Oracle Net configuration files which are used Naming method which is used (local tnsnames.ora) Allowed methods and priorities are defined in sqlnet.ora (NAMES.DIRECTORY_PATH) Success
  • 20. Oracle Net Configuration (5) – tnsping Checklist: Database Connection Issues 20 17.05.2022 Name can be resolved, but no listener is running on given port and host: Name cannot be resolved oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01 [..] Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = PDB01.trivadistraining.com))) TNS-12541: TNS:no listener Check if host and port are correct oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping PDB01A [..] Used parameter files: /u00/app/oracle/network/admin/sqlnet.ora TNS-03505: Failed to resolve name Check tnsnames.ora if entry exists
  • 21. Oracle Net Configuration (6) – Database Connection Checklist: Database Connection Issues 21 17.05.2022 Use SQL*Plus to check if the given database service is available: oracle@training19c:/u00/app/oracle/network/trc/ [TVDNCDB] tnsping TVDNCDB TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019 15:08:23 [..] Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = TVDNCDB.trivadistraining.com))) OK (0 msec) oracle@training19c:/u00/app/oracle/network/trc/ [rdbms19000] sqlplus system/manager@TVDNCDB SQL*Plus: Release 19.0.0.0.0 - Production on Sat May 11 15:05:43 2019 Version 19.3.0.0.0 Copyright (c) 1982, 2019, Oracle. All rights reserved. ERROR: ORA-12514: TNS:listener does not currently know of service requested in connect descriptor Listener is up, but there is no instance registered which provides the service
  • 22. Oracle Net Configuration (7) – Service Registration Checklist: Database Connection Issues 22 17.05.2022 When a database instance is started, it registers itself with the listener (PMON process (before 12c) or LREG process) – Parameter LOCAL_LISTENER As soon as the registration is complete, the listener is aware of the services which are provided by the database instance If you bounce the listener while the database is running, it can take up to 60 seconds before the database "renews" the registration. – This may lead to a (temporary) ORA-12514: – You can enforce the registration: ORA-12514: TNS:listener does not currently know of service requested in connect descriptor SQL> alter system register; System altered.
  • 23. Oracle Net Configuration (8) – Easy Connect Checklist: Database Connection Issues 23 17.05.2022 If you want to rule out name resolution via LDAP or tnsnames, you can try Easy Connect 1. Allow Easy Connect via sqlnet.ora 2. Test the connection with Easy Connect (Host:Port/Service) NAMES.DIRECTORY_PATH=(LDAP, TNSNAMES, EZCONNECT ) oracle@training19c:/u00/app/oracle/network/admin/ [TVDNCDB] tnsping training19c.trivadistraining.com:1521/PDB01.trivadistraining.com TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 11-MAY-2019 13:56:58 Copyright (c) 1997, 2019, Oracle. All rights reserved. Used parameter files: /u00/app/oracle/network/admin/sqlnet.ora Used EZCONNECT adapter to resolve the alias Attempting to contact (DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=PDB01.trivadistraining.com))(ADDRESS= (PROTOCOL=tcp)(HOST=192.168.56.108)(PORT=1521))) OK (0 msec)
  • 24. Oracle Net Configuration (9) – Timeout Checklist: Database Connection Issues 24 17.05.2022 With slow network connections, it can be helpful to check (and change) the timeout parameters sqlnet.ora Use "0" to disable a parameter Check your OS specific documentation for changing timeouts on OS level SQLNET.INBOUND_CONNECT_TIMEOUT=n # server only, default 60 seconds, # time allowed for authentication SQLNET.OUTBOUND_CONNECT_TIMEOUT=n SQLNET.RECV_TIMEOUT=n SQLNET.SEND_TIMEOUT=n TCP.CONNECT_TIMEOUT=n # default 60 seconds, time allowed to # establish a TCP connection
  • 25. Oracle Net Configuration (10) – tnsnames.ora in general Checklist: Database Connection Issues 25 17.05.2022 Recommendations – All entries should be full qualified (especially when using a names.default_domain) – Check for duplicate entries – Check for "bracket errors" – Errors in one entry may lead to name resolution failures in subsequent entries ==> add new entries at the end of the tnsnames.ora file Example entry PDB01.TRIVADISTRAINING.COM = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = training19c.trivadistraining.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = PDB01.trivadistraining.com) ) ) All names full qualified!
  • 26. Checklist: Database Connection Issues 26 17.05.2022 Check Connectivity with the Oracle Instant Client
  • 27. Oracle Instant Client Checklist: Database Connection Issues 27 17.05.2022 Lightweight Oracle Client Requires no administrator or root privileges during installation – Just unzip Modular configuration, e.g. modules – Required: "Basic Package " or "Basic Light Package" – SQL*Plus Package – JDBC Package – ODBC Package Download: https://www.oracle.com/technetwork/database/database-technologies/instant- client/downloads/index.html
  • 28. Connection Tests using Instant Client Checklist: Database Connection Issues 28 17.05.2022 In order to rule out configuration issues with your application, you can use instant client for testing connections – E.g. from your database server to your database server (using Oracle Net) – From your application server to the database server – Etc. Procedure 1. Download and unzip all required packages 2. Set environment variables 3. Use your own Oracle Net configuration (tnsnames.ora etc.) for testing (=> set TNS_ADMIN) 4. Test the connection
  • 29. Checklist: Database Connection Issues 29 17.05.2022 Check Oracle Client Version
  • 30. Oracle Client – Server Certification (1) Checklist: Database Connection Issues 30 17.05.2022 * 11.2.0.3 or 11.2.0.4 only ** was a supported combination, but is currently out of support Special = limited support (special contract required) Source: MOS note 207303.1 Client Server 19c/18c/12.2 12.1 11.2 (*) 11.1 10.2 19c/18c /12.2 OK OK OK NO NO 12.1 OK OK OK NO** Special 11.2 (*) OK* OK OK NO** Special 11.1 NO NO** NO** NO** NO** 10.2 NO Special Special NO** Special
  • 31. Oracle Client – Server Certification (2) Checklist: Database Connection Issues 31 17.05.2022 Older clients may be able to connect, but there may be limited functionality or "strange error messages" may occur The minimum client version which can be used to connect to an Oracle 12.2 database (or later) is Oracle 8i (8.1) Especially when using Oracle Net encryption (free with every edition of the database) older clients may no be able to connect This may lead to connection issues after upgrading a database! –  Check the client versions before upgrading a database!
  • 32. Oracle Client – Find out the client versions Checklist: Database Connection Issues 32 17.05.2022 select sc.client_version,sc.client_driver, s.machine,s.program,s.osuser,s.service_name,count(*) from gv$session s,gv$session_connect_info sc where sc.inst_id=s.inst_id and sc.sid=s.sid and sc.serial#=s.serial# and s.type<>'BACKGROUND' group by sc.client_version,sc.client_driver,s.machine,s.program,s.osuser,s.service_name order by sc.client_version,sc.client_driver,s.machine,s.program,s.osuser,s.service_name /
  • 33. Checklist: Database Connection Issues 33 17.05.2022 Check Password Versions
  • 34. Check Password Versions Checklist: Database Connection Issues 34 17.05.2022 Case-Sensitive Passwords – Introduced with Oracle 10g – Parameter SEC_CASE_SENSITIVE_LOGON as a workaround – Parameter deprecated since Oracle 12c Using SEC_CASE_SENSITIVE_LOGON will result in an ORA-32004 when starting the database instance – Solution: remove the parameter from the spfile ORA-32004: obsolete or deprecated parameter(s) specified for %s instance SQL> ALTER SYSTEM RESET sec_case_sensitive_logon scope=spfile sid='*';
  • 35. Password versions (1) Checklist: Database Connection Issues 35 17.05.2022 The algorithm for the password hashes was changed since Oracle 10c – There may be different password versions (= password hashes) stored in the database – A client needs a "compatible" password version in order to connect SQL select password_versions from dba_users; PASSWORD_VERSIONS ----------------- 10G 11G 12C 11G 12C [..]
  • 36. Password versions (2) – the problem Checklist: Database Connection Issues 36 17.05.2022 The parameter SQLNET.ALLOWED_LOGON_VERSION_SERVER determines, which password hashes are generated – Default in Oracle 12.2: 12 –  Only 11G + 12C Hashes will be generated –  10g-Clients cannot connect ORA-1017: invalid username/password; logon denied
  • 37. Password versions (3) – the solution Checklist: Database Connection Issues 37 17.05.2022 1. Set SQLNET.ALLOWED_LOGON_VERSION_SERVER = 8 -  all password hashes will be generated 2. Make the database generate new password hashes (for users which are used by Oracle 10g clients) 3. Users with Oracle 10g clients can connect  SQL> ALTER USER <user> identified by <EXISTING_PASSWORD>;
  • 38. Checklist: Database Connection Issues 38 17.05.2022 Oracle Net Logging & Tracing
  • 39. Introduction Checklist: Database Connection Issues 39 17.05.2022 Logging and tracing can provide more detailled information in order to diagnose connectivity issues Can be enabled on – Listener Level – Client Level – Server Level Tracing and logging can generate a huge number of large files, do not forget to disable it after the issue has been solved
  • 40. Listener.log (1) Checklist: Database Connection Issues 40 17.05.2022 Enable listener logging Listener.ora Location of the listener.log in ADR: Check the listener.log after each (failed) connection attempt for any error message Listener.log can become huge => resize it before testing, e.g. cp listener.log listener.log.backup; echo "" >listener.log # enable or disable listener.log LOGGING_LISTENER = ON # Logging parameters, ignored if ADR is used #LOG_DIRECTORY_LISTENER = /u00/app/oracle/network/log #LOG_FILE_LISTENER = listener.log $ORACLE_BASE/diag/tnslsnr/<hostname>/<listener_name>/trace
  • 41. Listener.log (2) - Example Checklist: Database Connection Issues 41 17.05.2022 11-DEC-2014 08:10:14 * (CONNECT_DATA=(CID=(PROGRAM=SQL Developer)(HOST=__jdbc__)(USER=mbg))(SERVER=DEDICATED)(SERVICE_NAME=TVD12. trivadistraining.com)) * (ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.1)(PORT=54163)) * establish * TVD12.trivadistraining.com * 0 11-DEC-2014 08:10:59 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=TVD12.trivadistraining.com)( CID=(PROGRAM=C:Program?FilesDellToad?for?Oracle?12.6?TrialToad.exe)(HO ST=LTMBG02)(USER=mbg))) * (ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.1)(PORT=54182)) * establish * TVD12.trivadistraining.com * 0
  • 42. Listener Tracing Checklist: Database Connection Issues 42 17.05.2022 The listener uses the ADR infrastructure by default For the classical version, the ADR must be deactivated in the LISTENER.ORA and the listener must be restarted (DIAG_ADR_ENABLED_LISTENER=OFF) Different trace levels are possible: – OFF (0), USER (4), ADMIN (8), or SUPPORT (16) DIAG_ADR_ENABLED_LISTENER = OFF TRACE_LEVEL_LISTENER = 16 TRACE_DIRECTORY_LISTENER = /u00/app/oracle/network/trc TRACE_FILE_LISTENER = listener.trc TRACE_TIMESTAMP_LISTENER = TRUE
  • 43. Server Logging Checklist: Database Connection Issues 43 17.05.2022 Logging parameters LOG_DIRECTORY_SERVER = /u00/app/oracle/network/log LOG_FILE_SERVER = sqlnet_server.log
  • 44. Server Tracing Checklist: Database Connection Issues 44 17.05.2022 Since Oracle 11g trace and log files are stored by the client and the server in the Automatic Diagnostic Directory (ADR) For the classical version, the ADR must be deactivated in the SQLNET.ORA Different trace levels are possible: – OFF (0), USER (4), ADMIN (8), or SUPPORT (16) The TRACE_*_SERVER parameters can then be set TRACE_LEVEL_SERVER = 16 TRACE_DIRECTORY_SERVER = /u00/app/oracle/network/trc TRACE_FILE_SERVER = sqlnet_server.trc TRACE_TIMESTAMP_SERVER = TRUE DIAG_ADR_ENABLED = OFF
  • 45. Client Logging Checklist: Database Connection Issues 45 17.05.2022 Logging Parameters Example: LOG_DIRECTORY_CLIENT = /u00/app/oracle/network/log LOG_FILE_CLIENT = sqlnet_client.log oracle@training19c:/u00/app/oracle/network/log/ [TVDNCDB] cat sqlnet_client.log *********************************************************************** Fatal NI connect error 12514, connecting to: (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=training19c.trivadistraining.com)(PORT=1521))(CONNECT_D ATA=(SERVER=DEDICATED)(SERVICE_NAME=TVDNCDB.trivadistraining.com)(CID=(PROGRAM=sqlplus)(HOST=trai ning19c.trivadistraining.com)(USER=oracle)))) VERSION INFORMATION: TNS for Linux: Version 19.0.0.0.0 - Production TCP/IP NT Protocol Adapter for Linux: Version 19.0.0.0.0 - Production Version 19.3.0.0.0 Time: 11-MAY-2019 15:05:43 Tracing to file: /u00/app/oracle/network/trc/sqlnet_client_19495.trc Tns error struct: ns main err code: 12564 [..]
  • 46. Client Tracing Checklist: Database Connection Issues 46 17.05.2022 For the classical version, the ADR must be deactivated in the SQLNET.ORA Different trace levels are possible: – OFF (0), USER (4), ADMIN (8), or SUPPORT (16) The TRACE_*_SERVER parameters can then be set DIAG_ADR_ENABLED = OFF TRACE_LEVEL_CLIENT = 16 TRACE_DIRECTORY_CLIENT = /u00/app/oracle/network/trc TRACE_FILE_CLIENT = sqlnet_client.trc TRACE_TIMESTAMP_CLIENT = TRUE
  • 47. Checklist: Database Connection Issues 47 17.05.2022 Miscellaneous
  • 48. Increase the Array Fetch Size Checklist: Database Connection Issues 48 17.05.2022 Not in order to solve connection issues, but to improve performance Increasing the array size will – Reduce the number of fetches – Reduce the number of packets to be transferred Default value is 15 Changing the array fetch size is not always an option (think of 3rd party software) SQLPLUS> SET ARRAYSIZE 49
  • 49. Network Performance - Packet Size – MTU & SDU Checklist: Database Connection Issues 49 17.05.2022 Both are performance related settings MTU (Maximum Transmission Unit) – Default: 1460 bytes – Enlarging this value can help to reduce the number of packets sent over the network – All network components must support higher values and have to be changed accordingly SDU (Session data unit) – Changing the "Session data unit" size can help to reduce Oracle Net related wait events ('SQL*Net message to client' and 'SQL*Net more data to client') – Setting the default SDU size on client and server in sqlnet.ora – Or use "(SDU_SIZE=8192)" in listener.ora and tnsnames.ora DEFAULT_SDU_SIZE=8192
  • 50. Checklist: Database Connection Issues 50 17.05.2022 More information
  • 51. MOS-Notes (1) Checklist: Database Connection Issues 51 17.05.2022 Oracle Net Diagnostics (Doc ID 834822.1) SQL*Net & Oracle Net Services - Tracing and Logging at a Glance (Doc ID 219968.1) How to Enable Oracle SQL*Net Client , Server , Listener , Kerberos and External procedure Tracing from Net Manager (Doc ID 395525.1) How To Limit Connections Generating Trace when Oracle Net Server Enabled (Doc ID 401134.1) Intended Usage of the TNSPING Utility (Doc ID 787848.1) How to Match Oracle Net Client and Server Trace Files (Doc ID 374116.1) How to Perform the Equivalent of SQL*Net Client Tracing with Oracle JDBC Thin Driver (Doc ID 793415.1) Shared Server (MTS) Diagnostics (Doc ID 1005259.6) How to Diagnose Slow TNS Listener / Connection Performance (Doc ID 557416.1) Listener Hanging - Information to Get For Resolving or Troubleshooting (Doc ID 230156.1) Oracle Net (SQL*Net) Timeout Parameters (Doc ID 1560775.1)
  • 52. MOS-Notes (2) Checklist: Database Connection Issues 52 17.05.2022 Oracle Net Diagnostic Examples (Doc ID 1384945.1) How to Reduce the TCP/IP Timeout for Oracle Net on Solaris (Doc ID 275189.1) How to Configure Linux OS Ethernet TCP/IP Networking (Doc ID 132044.1) Change MTU Size in Oracle Linux (Doc ID 2520148.1) The relation between MTU (Maximum Transmission Unit) and SDU (Session Data Unit) (Doc ID 274483.1) SQL*Net Packet Sizes (SDU & TDU Parameters) (Doc ID 44694.1) Troubleshooting Waits for 'SQL*Net message to client' and 'SQL*Net more data to client' Events from a Performance Perspective (Doc ID 1404526.1) Oracle Net Performance Tuning (Doc ID 67983.1) Starting With Oracle JDBC Drivers - Installation, Certification, and More! (Doc ID 401934.1) SQL*Net & Oracle Net Services - Tracing and Logging at a Glance (Doc ID 219968.1) RAC/SCAN: How to set SDU, Queuesize and Other Net Parameters for RAC Listeners (Doc ID 1292915.1)
  • 53. Oracle Documentation & Other Links Checklist: Database Connection Issues 53 17.05.2022 Documentation – Net Services Administator's Guide - Part III Testing and Troubleshooting Oracle Net Services https://docs.oracle.com/en/database/oracle/oracle-database/19/netag/part-III-test-and- troubleshoot-oracle-net-services.html#GUID-E8B29E61-3236-486B-AB89-665215E86CFA Other Links – http://www.oracledbaplusbigdata.com/2018/01/27/sqlnet-ora-logging-and-tracing/
  • 54. Questions and Answers Markus Flechtner Principal Consultant Phone +49 211 5866 64725 Markus.Flechtner@Trivadis.com @markusdba http://markusdba.de Download the slides from https://www.slideshare.net/markusflechtner Please don‘t forget the session evaluation – Thank you! 17.05.2022 Checklist: Database Connection Issues 54