Oracle 12c Multi Process Multi Threaded

BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA
HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH
Oracle 12c: Multi Process Multi Threaded
A closer look at the multi-process multi-threaded model for Oracle
on Linux/Unix
Markus Flechtner
Senior Consultant
Flechtner_Oracle_12c_multi_process_multi_t
hreaded.pptx

Our company.
Oracle 12c: Multi Process Multi Threaded3 12/24/16
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COPENHAGEN
MUNICH
LAUSANNE
BERN
ZURICH
BRUGG
GENEVA
HAMBURG
DÜSSELDORF
FRANKFURT
STUTTGART
FREIBURG
BASLE
VIENNA
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About Markus Flechtner
Senior Consultant, Trivadis, Duesseldorf/Germany, since April 2008
Discipline Infrastructure Database @Trivadis
Working with Oracle since the 1990’s
– Development (Forms, Reports, PL/SQL)
– Support
– Database Administration
Focus
– Oracle Real Application Clusters
– Database Migration Projects
Teacher
– O-RAC – Oracle Real Application Clusters
– O-NF12CDBA – Oracle 12c New Features for the DBA
Blog:
http://markusdba.de/
@markusdba

Agenda
1. The problem & existing solutions
2. New in Oracle Database 12c: THREADED_EXECUTION
3. Architecture
4. Performance
5. Threaded Execution in the daily DBA business
6. Pros & Cons

The problem & existing solutions

The problem & existing solutions (1)
In the dedicated server achitecture on Unix/Linux:
– every client session has got its own server process
– these processes need memory and processor time
– there are many context switches
Many applications
– Keep database sessions open and rarely execute SQL statements
Result
– Overhead on the database server
– Waste of system resources

Existing solutions
– Shared Server (Multithreaded Server)
– Database Resident Connection Pooling (DRCP)
è not for all applications
– Universal Connection Pool (UCP)
– Connection Pools in general (Application Server)
All these solutions affect client sessions only

Overview on existing solutions
• From Oracle Database 12c Administrators Guide © Oracle Corporation

The “Multithreaded Oracle Process Model” does not replace
these solutions but is a new method to reduce the resource
consumption of a database instance on a Linux/Unix
database server.

New in Oracle Database 12c:
THREADED_EXECUTION
"Multithreaded Oracle Process Model"

Processes vs. Threads
Process
– A process is an instance of a computer program that is being
executed. It contains the program code and its current activity.
Depending on the operating system (OS), a process may be
made up of multiple threads of execution that execute
instructions concurrently
Threads
– A thread of execution is the smallest sequence of
programmed instructions that can be managed independently
by a scheduler ..
Source: Wikipedia (http://en.wikipedia.org)
Process
Thread 1
Thread 2

Multithreaded Oracle Process Model (1)
The “Multithreaded Oracle Process Model” on Unix/Linux enables the database instance
to run instance processes as operating system threads
– Similar to Oracle on Windows
– No additional license costs; works on SE1, SE2, SE and EE
Configuration:
– Restart the instance
– Result: (most) background processes and local connections run as OS threads
ALTER SYSTEM SET threaded_execution=TRUE SCOPE=spfile SID='*'

Multithreaded Oracle Process Model (2)
For remote clients which connect via Oracle Net a parameter for the listener must be set
in the listener.ora file:
– Restart the listener afterwards
If you want to run remote clients in threaded and non-threaded mode, a second listener is
required
– Different port and/or host name resp. IP address
– DEDICATED_THROUGH_BROKER_<new_listener>=OFF (default)
DEDICATED_THROUGH_BROKER_<listener_name>=ON

Multithreaded Oracle Process Model (3) – DB Connect
Conn.Broker
(Thread)
SGA
LISTENER
➊
➍
➎
➋
➌
Thread for
DB Session

Architecture

Architecture (1) - Processes
Process list of an Oracle instance with THREADED_EXECUTION
“Threaded Sessions” are “hidden” in the "ora_u<nnn>_<SID>“-processes
oracle@te:~/ [TEST] ps –ef |grep $ORACLE_SID
oracle 6593 1 0 10:02 ? 00:00:00 ora_pmon_TEST
oracle 6595 1 0 10:02 ? 00:00:00 ora_psp0_TEST
oracle 6597 1 14 10:02 ? 00:00:03 ora_vktm_TEST
oracle 6601 1 23 10:02 ? 00:00:05 ora_u004_TEST
oracle 6607 1 99 10:02 ? 00:00:22 ora_u005_TEST
oracle 6613 1 0 10:02 ? 00:00:00 ora_dbw0_TEST

Architecture (2) - Processes
oracle@te:~/ [TEST] ps –ef |grep ora_u00
oracle 31220 1 2 21:18 ? 00:00:03 ora_u004_TEST
oracle 31226 1 11 21:18 ? 00:00:13 ora_u005_TEST
oracle@te:~/ [TEST] pidstat -t -p 31220
Linux 3.8.13-26.2.1.el6uek.x86_64 (te.markusflechtner.vm) 03/22/2014 _x86_64_ (4 CPU)
09:20:45 PM TGID TID %usr %system %guest %CPU CPU Command
09:20:45 PM 31220 - 0.01 0.01 0.00 0.02 3 ora_scmn_test
09:20:45 PM - 31220 0.00 0.00 0.00 0.00 3 |__ora_scmn_test
09:20:45 PM - 31221 0.00 0.00 0.00 0.00 1 |__oracle
09:20:45 PM - 31222 0.00 0.00 0.00 0.00 0 |__ora_gen0_test
09:20:45 PM - 31223 0.00 0.00 0.00 0.00 2 |__ora_mman_test
09:20:45 PM - 31229 0.00 0.00 0.00 0.00 3 |__ora_dbrm_test
09:20:45 PM - 31233 0.00 0.00 0.00 0.00 1 |__ora_lgwr_test
09:20:45 PM - 31234 0.00 0.00 0.00 0.00 0 |__ora_ckpt_test
09:20:45 PM - 31235 0.00 0.00 0.00 0.00 3 |__ora_lg00_test
09:20:45 PM - 31236 0.00 0.00 0.00 0.00 3 |__ora_smon_test
09:20:45 PM - 31237 0.00 0.00 0.00 0.00 2 |__ora_lg01_test
09:20:45 PM - 31239 0.00 0.00 0.00 0.00 3 |__ora_lreg_test

Architecture (3) – V$PROCESS
SQL> select spid,stid,execution_type,pname from v$process
2 where spid is not null and (execution_type=‘PROCESS’ or pname in
3 ('PMON','SMON','DBW0','PSP0','VKTM','MMON','RECO','LGWR',’SCMN’));
SPID STID EXECUTION_ PNAME
------------------------ ------------------------ ---------- -----
6593 6593 PROCESS PMON
6595 6595 PROCESS PSP0
6597 6597 PROCESS VKTM
6601 6614 THREAD LGWR
6601 6601 THREAD SCMN
6601 6618 THREAD SMON
6607 6621 THREAD MMON
6607 6607 THREAD SCMN
6607 6619 THREAD RECO
6613 6613 PROCESS DBW0

Architecture (4)
The “SCMN”-Thread is the “thread listener” or “thread coordinator” within the process
The threaded sessions remain “dedicated server” sessions:
PGA is allocated from the shared pool (like with “Shared Server")
SQL> select p.execution_type,s.server,count(*)
2 from v$process p,v$session s
3 where s.paddr=p.addr
4 group by p.execution_type,s.server;
EXECUTION_ SERVER COUNT(*)
---------- --------- ----------
THREAD DEDICATED 38
PROCESS DEDICATED 4

Architecture (5)
Ora_uNNN processes are terminated after beeing idle for 30 seconds
Every threaded session needs a processes slot (=> Parameter PROCESSES)
(è TNS-12602 “Connection pooling limit reached.”)

Architecture (6) – Memory Consumption
In average:
18% less memory
consumption with
„THREADED_EXECUTION“

Architecture (7) – Connection Broker
Threaded Execution requires a Connection Broker
The new parameter CONNECTION_BROKERS is set automatically when
THREADED_EXECUTION=TRUE
SQL> show parameter connection_brokers
NAME TYPE VALUE
------------------ ------- ----------------------------------------
connection_brokers string ((TYPE=DEDICATED)(BROKERS=1)),
((TYPE=EMON)(BROKERS=1))

Architecture (8) – Connection Broker & Listener
lsnrctl services
[..]
Service "TEST.markusflechtner.vm" has 1 instance(s).
Instance "TEST", status READY, has 2 handler(s) for this service...
Handler(s):
"N000" established:1 refused:0 state:ready
CMON <machine: te.markusflechtner.vm, pid: 1649_1668>
(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=34848))
"DEDICATED" established:0 refused:0 state:ready
LOCAL SERVER
[..]

Architecture (9) – Connection Broker & Listener
oracle@te:~/ [TEST] ps –ef |grep 1649
oracle 1649 1 9 19:24 ? 00:05:12 ora_u005_TEST
SQL> select spid,stid,pname,execution_type from v$process
2 where spid=1649 and stid=1668;
SPID STID PNAME EXECUTION_TYPE
---------------- ---------------- ----- --------------
1649 1668 N000 THREAD

Architecture (10) - Miscellaneous
Threaded Execution & CPU usage
– No essential difference to "Non-Threaded-Execution"
Threaded Execution & Connect Time
– No essential difference to "Non-Threaded-Execution"
Threaded Execution on Windows
– The parameter has no effect
Multitenant Databases
– An OS process can contain sessions of multiple PDBs

Performance

Performance (1) – Test Environment
Host
– Notebook Lenovo W510 / 32 GB RAM / SSD
– Oracle Linux 6.5
Virtual Server (VirtualBox)
– 16 GB RAM
Oracle Database
– Oracle 12.1.0.1
– 6000M SGA / 2000M PGA
– Non-CDB-Architecture

Performance (2) – Test with Swingbench
Test Software
– Swingbench 2.5.0.99
(www.dominicgiles.com)
– 3 tests with
50 - 900 sessions,
average of transactions
per second

Performance (3) - Results

Performance (4) – Other tests
Oracle presentation on „Real Application Testing":
– 5% better performance with THREADED_EXECUTION
Thomas Bordeau: http://blog.arkzoyd.com/2014/01/17/oracle-multithreaded-does-it-worth-
a-try/
– Another test with SwingbenchJ
Overall result:
èBetter performance
èBetter scalability

Threaded Execution
in the daily DBA business

OS Authentication (1)
OS authentication is not supported with threaded execution
– è ORA-1017 invalid username ..
– Password File required
– è Startup/Shutdown scripts have to be changed
Some Oracle tools require "Non-Threaded Execution"
– dbca
– dbua
– datapatch

OS Authentication (2) - Workaround
Store the password in a wallet
In short (see MOS-Note 340559.1 for details)
# create wallet
mkstore -wrl <wallet_location> -create
# add db authentication information
mkstore -wrl <wallet_location> -createCredential <db_connect_string>
<username> <password>
# add the following lines to sqlnet.ora
WALLET_LOCATION =
(SOURCE =
(METHOD = FILE)
(METHOD_DATA = (DIRECTORY = <wallet_location_directory>)))
SQLNET.WALLET_OVERRIDE = TRUE
Connect to the DB using sqlplus sys/@<DB_Connect_String>

OS Authentication (3) – Other workarounds
sqlplus
/@"(ADDRESS=(PROTOCOL=BEQ)(PROGRAM=oracle)(ARGS='(ADDRESS=(PROTOCOL=BEQ))'
))" AS SYSDBA
# the way the clusterware agent connects to the instance
sqlplus
/@"(DESCRIPTION=(ADDRESS=(PROTOCOL=beq)(PROGRAM=/u00/app/oracle/product/12
.1.0.2/bin/oracle)(ARGV0=oracleGG03)(ENVS='ORACLE_HOME=/u00/app/oracle/pro
duct/12.1.0.2,ORACLE_SID=TEST,LD_LIBRARY_PATH=,ORACLE_BASE=')(ARGS='(DESCR
IPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))')(CONNECT_DATA=(SID=TEST))))"
AS SYSDBA

SQL Tracing
What‘s the name of the trace file?
è The filename contains SPID and STID
SQL> select spid,stid,execution_type,tracefile from v$process;
SPID STID E_TYPE TRACEFILE
----- ----- ------- ------------------------------------------------------------------
NONE /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_ora_0.trc
6961 6961 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_pmon_6961.trc
6963 6963 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_psp0_6963.trc
6965 6965 PROCESS /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_vktm_6965.trc
6969 6971 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_gen0_6969_6971.trc
6969 6969 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_scmn_6969_6969.trc
6969 6972 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_mman_6969_6972.trc
6975 7000 THREAD /u00/app/oracle/diag/rdbms/test/TEST/trace/TEST_ora_6975_7000.trc
..

How to kill database sessions?
As usual, sessions are identified via SID and SERIAL# in V$SESSION
Kill on database/instance level works fine:
But „kill -9 <spid>“ on OS level is not a good idea L
A thread cannot be killled from without the corresponding OS process
„kill -6 <stid>“ (SIGABRT) can help
– è find out the thread id via V$PROCESS or „pidstat“
– è execute „kill -6 <stid>“
ALTER SYSTEM KILL SESSION ‘<sid>,<serial#>‘;

Pros & Cons

Pros & Cons - Pro
Easy setup
Reduced memory consumption
Reduced number of processes on OS level
– è less context switches
Performance
– Equal or better than "non-threaded execution“
Scalability
– Equal or better than „non-threaded execution“
Statements regarding
performance and scalability
have to be verified in each
individual case!
Test Threaded Execution with
your application before you use
it!

Pros & Cons - Con
Missing OS authentication
– Scripts have to be changed
„kill -9“ does not work
srvctl (RAC) does not work
– Unpublished bug

Summary
There‘s not much information from Oracle on this feature
It is not really clear, why Oracle introduced this feature
There is no experience from customer projects so far, but if you accept the disadvantages
(missing OS authentication, killing sessions on OS level), the „Multithreaded Multi
Threaded“-model can make sense, if
– Your application does not support connection pools
– Your database is low on memory
But „Threaded execution“ cannot replace connection pools

§MOS-Note 1639445.1: 12c: Threaded_execution=true Prevents OS Login As Sysdba
§MOS-Note 1958348.1: Multi-Threaded Oracle Model
§MOS-Note 340559.1: „Using The Secure External Password Store“
§Oracle Presentation „Maximizing Database Performance Using Database Replay“
§http://blog.arkzoyd.com/2014/01/17/oracle-multithreaded-does-it-worth-a-try/
§http://dbwhisperer.wordpress.com/2013/10/04/multi-threaded-oracle-12c-Architektur-on-linux-2/
Further Information

Questions and Answers
Markus Flechtner
Senior Consultant
Phone +49 211 5866 6470
Markus.Flechtner@Trivadis.com
@markusdba http://markusdba.de
Download the slides from http://www.slideshare.net/markusdba
Please don‘t forget the session evaluation – Thank you!
12/24/16 Oracle 12c: Multi Process Multi Threaded44

Oracle 12c Multi Process Multi Threaded

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