The document discusses configuring and managing a read-only standby Oracle 8i database. It describes standby database basics, new Oracle 8i capabilities for standby databases, and how to set up a standby database including initial configuration, starting up the standby instance, and ongoing operational issues. It also provides an example of recovering a standby database after a primary database change and the resulting state of data on the standby.

1. 04/15/2000
Configuring and Managing an Oracle 8i
Read-Only Standby Database
Bill Schott
Detroit Edison
Prepared for presentation at the ECO/SEOC 2000 Conference, March 21, 2000
© 2000, The Detroit Edison Company, All Rights Reserved

2. 04/15/2000
Purpose and Overview
uReview Standby Database Basics
uNew Oracle 8i Capabilities
uHow to Setup
uOperational Issues
uTroubleshooting
1

3. 2
Why Use a Standby Database?
u Provide a current, ready-to-go
database should regular server
fail
u Hardware Independent,
Software solution
u Remote Backup Data Center
2

4. 3
Standby Database - The Picture
Server A
PR01
Instance
PR01
Archive
Storage
Server B
Archive Logs
Via Net8
SB01
Instance
PR01
Archive
Storage

5. 4
Standby Basics
u Start with a copy of Database
u Keep it in continuous recovery mode
u Feed and apply archive logs as soon as
generated
u Standby only as good as last applied
Archive Log

6. 5
Utilizing Wasted Hardware
u Failures are infrequent
u Lots of $$$ tied up
u Demand for reports
u Regular
u Ad Hoc
u What if...Open Read Only

7. 6
New Capabilities in Oracle8i
u Alter Database Open Read Only
u Managed Recovery
u Archive Log Path via Net8
u Up to 5 Archive Log Paths
u Mandatory or Optional
u Enable or Defer
u Locally Managed Tablespace

8. 7
Getting Started - Planning
u Plan your Filenames
(DB_FILE_NAME_CONVERT)
u Setup Standby Server
u Oracle version and patch
level
u Physical Path name mapping
u init.ora for Standby Instance

9. 8
PR01 Archive Log Parameters
u log_archive_max_processes = 2 (or more)
u log_archive_dest_1= 'LOCATION=
/oracle/a01/pr01/archive/arch mandatory reopen=5'
u log_archive_dest_state_1 = enable
u log_archive_dest_2= 'SERVICE=sb01 optional
reopen=60’
u log_archive_dest_state_2 = enable
u log_min_succeed_dest=1

10. 9
Standby Init.Ora Details
u Different Values for Redo Logs and Controlfiles
u New Parameters
u standby_log_dest=(same as log_archive_dest)
u log_archive_format=arch%t_%s.dbf
u Remove Dual Archive Log paths
u Audit_trail=FALSE or OS
u All others Identical
u compatible=8.1.5 in both

11. 10
Getting Started - Preparing
u Create Tablespace TEMP tempfile ‘…’ extent
management local uniform size 5m;
u Copy primary database files to Standby system
u ALTER DATABASE CREATE STANDBY
CONTROLFILE AS 'standby.ctl';
u Rcp standby.ctl to location of all control files on
Server B.
u Alter System Switch Logfile

12. 11
Getting Started - Starting up
u STARTUP NOMOUNT pfile=initsb01.ora
u ALTER DATABASE MOUNT STANDBY
DATABASE;
u RECOVER STANDBY DATABASE;
u ALTER DATABASE OPEN READ ONLY;

13. 12
Operational Issues - Cautions
u Always keep Standby Instance running
u If log switch on pr01 while sb01 not running, must
manually copy archive log and RECOVER
STANDBY DATABASE.
u Any incomplete recovery on pr01 invalidates sb01

14. 13
Operational Issues - Updating
u To update and re-open read only:
u RECOVER MANAGED STANDBY DATABASE
TIMEOUT 1;
u ALTER DATABASE OPEN READ ONLY;
u To use as a pure standby database,
u RECOVER MANAGED STANDBY DATABASE;

15. 14
Operational Issues - Troubleshooting
u Architecture appears solid
u Able to recover every mess I’ve tried.
u Use Creating new Standby Controlfile as a
Last Resort.

16. 15
Operational Issues - Physical Changes
u New Tablespace or Data File
u rcp file to Server B *before* attempting recovery
u Managed Recovery WILL FAIL;
u alter database create datafile '/oracle/d11/pr01/users02.dbf'
as '/oracle/d11/pr01/users02.dbf';
u Resume Managed Recovery
u File Resizing is not a problem.

17. 16
An Interesting Example - PR01 Commands
SQL> Alter Tablespace users add datafile ‘…pr01/users02…’ size 2M;
SQL> Create table ac4 Tablespace users as select * from ac3;
SQL> @extents_by_file users02
FID File Name (/oracle/...) Block Segment Name ExID Bytes
---- ------------------------ ------- ------------- ---- -------
8 d11/pr01/users02 2 AC4 1 143,360
d11/pr01/users02 37 AC4 2 131,072
d11/pr01/users02 69 AC4 3 131,072
SQL> select {…} from dba_segments where segment_name = 'AC4';
OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME
------ ------------ ------------ ---------------
ORACLE AC4 TABLE USERS
SQL> select count(*) from oracle.ac4;
712

18. 17
An Interesting Example - Recover SB01
SQL> recover managed standby database timeout 1;
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 8 needs more recovery to be consistent
ORA-01110: data file 8: '/oracle/d11/dvd6/users02.dbf'
ORA-16016: archived log for thread 1 sequence# 213 unavailable
WHAT WAS WRITTEN TO THE ALERT LOG:
Media Recovery Start: Managed Standby Recovery
WARNING! Recovering data file 8 from a fuzzy file. If not the current file
it might be an online backup taken without entering the begin backup command.
Media Recovery Log
Media Recovery Log /oracle/x01/dv08/archive/arch1_211.dbf
Media Recovery Log /oracle/x01/dv08/archive/arch1_212.dbf
Media Recovery Waiting for thread 1 seq# 213
Thu Jul 29 09:35:25 1999
Wait timeout: thread 1 sequence# 213
ORA-1547 signalled during: ALTER DATABASE RECOVER managed standby database ...

19. 18
An Interesting Example - Recover SB01
Continuing the recovery of SB01 from the earlier slide…
SQL> connect internal;
Connected
SQL> alter database create datafile /oracle/d11/pr01/users02.dbf’ as
'/oracle/d11/pr01/users02.dbf';
SQL> recover managed standby database timeout 1;
ORA-00283: recovery session canceled due to errors
ORA-16016: archived log for thread 1 sequence# 213 unavailable
SQL> alter database open read only;
Database altered.

20. 19
An Interesting Example - SB01 Queries
SQL> select count(*) from oracle.ac4;
ERROR at line 1: ORA-00942: table or view does not exist
SQL> @extents_by_file users02
FID File Name (/oracle/...) Block Segment Name ExID Bytes
---- ------------------------ ------- ------------- ---- -------
8 d11/pr01/users02 2 AC4 1 143,360
d11/pr01/users02 37 AC4 2 131,072
d11/pr01/users02 69 AC4 3 131,072
SQL> select {…} from dba_segments where segment_name = 'AC4';
OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME
------ ------------ ------------ ---------------
ORACLE AC4 TABLE USERS
SQL> descr oracle.ac4
ERROR: ORA-04043: object oracle.ac4 does not exist

21. 20
An Interesting Example - What Happened?
u What happened?
u How can a table be there, but
not exist?

22. 21
An Interesting Example - Log Switch
u What happened?
u How can a table be there, but
not exist?
u Lesson Learned: If you want
your Standby to look like your
primary, force a log switch
before Managed recovery

23. 22
Summary, Commentary, Conclusions
u Standby Database Support has matured
greatly in Oracle8i
u Open Read Only is a powerful tool
u Requires care to setup properly
u Some operational issues
u No showstopper bugs encountered
u Documentation is pretty good
u Remember to force log switch

24. 23
For More Information...
u Email address: bschott@corecomm.net
u Web page: www.corecomm.net/
~bschott/standby.html

25. 24
The ECO/OUR Conference is moving to the
fall in 2001
u The Conference will be held at the Opryland Hotel in
Nashville, TN
u Dates are September 30 thru October 3, 2001
u For more information call 910 452-0006 or visit us
on the web at www.oracle-users.com