04/15/2000

Configuring and Managing an Oracle 8iRead-Only Standby Database

Bill SchottDetroit Edison

Prepared for presentation at the ECO/SEOC 2000 Conference, March 21, 2000© 2000, The Detroit Edison Company, All Rights Reserved

04/15/2000

Purpose and Overview

uReview Standby Database BasicsuNew Oracle 8i CapabilitiesuHow to SetupuOperational IssuesuTroubleshooting

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Why Use a Standby Database?u Provide a current, ready-to-go

database should regular serverfail

u Hardware Independent,Software solution

u Remote Backup Data Center

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Standby Database - The Picture

Server A

PR01

Instance

PR01ArchiveStorage

Server B

Archive Logs

Via Net8

SB01

Instance

PR01ArchiveStorage

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Standby Basicsu Start with a copy of Database

u Keep it in continuous recovery mode

u Feed and apply archive logs as soon asgenerated

u Standby only as good as last appliedArchive Log

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Utilizing Wasted Hardwareu Failures are infrequent

u Lots of $$$ tied up

u Demand for reports

u Regular

u Ad Hoc

u What if...Open Read Only

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New Capabilities in Oracle8iu 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

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Getting Started - Planningu Plan your Filenames

(DB_FILE_NAME_CONVERT)

u Setup Standby Server

u Oracle version and patchlevel

u Physical Path name mapping

u init.ora for Standby Instance

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PR01 Archive Log Parametersu 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 optionalreopen=60’

u log_archive_dest_state_2 = enable

u log_min_succeed_dest=1

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Standby Init.Ora Detailsu 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

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Getting Started - Preparingu Create Tablespace TEMP tempfile ‘…’ extent

management local uniform size 5m;

u Copy primary database files to Standby system

u ALTER DATABASE CREATE STANDBYCONTROLFILE AS 'standby.ctl';

u Rcp standby.ctl to location of all control files onServer B.

u Alter System Switch Logfile

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Getting Started - Starting upu STARTUP NOMOUNT pfile=initsb01.ora

u ALTER DATABASE MOUNT STANDBYDATABASE;

u RECOVER STANDBY DATABASE;

u ALTER DATABASE OPEN READ ONLY;

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Operational Issues - Cautionsu Always keep Standby Instance running

u If log switch on pr01 while sb01 not running, mustmanually copy archive log and RECOVERSTANDBY DATABASE.

u Any incomplete recovery on pr01 invalidates sb01

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Operational Issues - Updatingu To update and re-open read only:

u RECOVER MANAGED STANDBY DATABASETIMEOUT 1;

u ALTER DATABASE OPEN READ ONLY;

u To use as a pure standby database,

u RECOVER MANAGED STANDBY DATABASE;

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Operational Issues - Troubleshootingu Architecture appears solid

u Able to recover every mess I’ve tried.

u Use Creating new Standby Controlfile as aLast Resort.

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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.

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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

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An Interesting Example - Recover SB01

SQL> recover managed standby database timeout 1;ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error belowORA-01194: file 8 needs more recovery to be consistentORA-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 RecoveryWARNING! Recovering data file 8 from a fuzzy file. If not the current fileit might be an online backup taken without entering the begin backup command.Media Recovery LogMedia Recovery Log /oracle/x01/dv08/archive/arch1_211.dbfMedia Recovery Log /oracle/x01/dv08/archive/arch1_212.dbfMedia Recovery Waiting for thread 1 seq# 213Thu Jul 29 09:35:25 1999Wait timeout: thread 1 sequence# 213ORA-1547 signalled during: ALTER DATABASE RECOVER managed standby database ...

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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 errorsORA-16016: archived log for thread 1 sequence# 213 unavailable

SQL> alter database open read only;

Database altered.

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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

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An Interesting Example - What Happened?u What happened?

u How can a table be there, butnot exist?

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An Interesting Example - Log Switchu What happened?

u How can a table be there, butnot exist?

u Lesson Learned: If you wantyour Standby to look like yourprimary, force a log switchbefore Managed recovery

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Summary, Commentary, Conclusionsu 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

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For More Information...u Email address: bschott@corecomm.net

u Web page: www.corecomm.net/~bschott/standby.html

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The ECO/OUR Conference is moving to thefall in 2001u 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 uson the web at www.oracle-users.com