11g(R1/R2) Data guard EnhancementsSuresh Gandhi

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Agenda

What is DATA GUARD ? Types of Data Guard Databases 11g Release 1 Enhancements 11g Release 2 Enhancements Active Data guard Snapshot Standby Database More Features Rolling Upgrade and Physical Standby Q&A

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Data Guard Overview

Data Guard

Standby Plus more

High Availability & Disaster Recovery Solution

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Provides ….

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Data guard Databases

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11G R1 Enhancements

Release 1 New

Features

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R2 - Enhancements

Release 2 New

Features

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R2- New Features

Release 2 New

Features

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Active and Snapshot Standby

Traditional Functionality until 10g11g Active DataGuard11g Snapshot Standby

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Active Data Guard Benefits

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Turn on Physical Standby to Active StandbyStop redo apply

Database in standby mount

mode

Open readonly

Open mode changed to read

only

Start the redo apply again using

log file (SRL’s)

Status changed to read only apply

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Turn on Physical Standby to Snapshot StandbyOnce sync check, convert standby to

snapshot

Open database

Read write mode

Need to close database

Switched back to physical standby

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Additional Info – Active / Snapshot

WHAT OPERATION ALLOWED IN ACTIVE DATA GUARD ? SELECT statements Complex queries Calling of stored procedures Use of database links to redirect DML to Primary Use of stored procedures to call remote stored procedures via database links Use of SET ROLE Use of ALTER SESSION and ALTER SYSTEM No Datatypes restrictions like Logical Standby Additional TEMPFILES can be created for Sorts Flashback Query : SELECT … AS OF <SCN> Additional License

• SOME IMPORTANT POINTS FOR SNAPSHOT STANDBY DATABASE

• PHYSICAL STANDBY DATABASE SHOULD BE IN FLASHBACK MODE

• NO REAL TIME QUERY OR DATA • NO FAST START FAILOVER IN THIS MODE • NO SWITCHOVER/FAILOVER UNTIL

CONVERTED TO PHYSICAL STANDBY • Free of Licence• POINTS

1. Configure the Flash Recovery Area 2. Set the Retention Target

3. Enable Flashback Database

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10g Equivalent Snapshot commandsPrepare the physical standby database to be activatedSQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=20G;SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='/arch/oradata'

Prepare the primary database to have the physical standby be diverged.

Archive the current log file.

SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;

Cancel Redo Apply and create a guaranteed restore point.SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;SQL> CREATE RESTORE POINT restore_pt GUARANTEE FLASHBACK DATABASE;

Activate the physical standby database.

SQL> ALTER DATABASE ACTIVATE STANDBY DATABASE;SQL> STARTUP MOUNT FORCE;SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;SQL> ALTER DATABASE OPEN

Revert the ac4vated database back to a physical standby database.SQL> STARTUP MOUNT FORCE;SQL> FLASHBACK DATABASE TO RESTORE POINT restore_pt;SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY;SQL> STARTUP MOUNT FORCE;

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DATGUARD – Still More Features

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More Features – RMAN Active database Duplication

RMAN> run {allocate channel prmy1 type disk;allocate channel prmy2 type disk;allocate channel prmy3 type disk;allocate channel prmy4 type disk;allocate auxiliary channel repstby type disk;duplicate target database for standby from active database spfileparameter_value_convert 'emrep','repstby'set db_unique_name='repstby'set db_file_name_convert='C:\','F:\'set log_file_name_convert='C:\','F:\';}

Steps–Create a pfile with only db_name=stby–Create directory structure for datafile locations–Create directory structure for dump locations–Create a password file (must match with target)–Listener & Tnsnames entries for new standby database–Startup nomount with pfile–Run the rman command in other box

Log File Duplicate_Database_log.txt

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More Features – Redo Compression

Requires Advanced Compression features Compress redo as it is transmitted data Automatically compress the data as it only resolves gaps Helpful and useful in bandwidth constrained locations Syntax:-

LOG_ARCHIVE_DEST_2=‘Service=stby Async compression=ENABLE’

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More Features – Heterogenous database support

Oracle 10g Dataguard support mixed environments 32bit and 64 bit configuration

Oracle 11G Dataguard supports mixed Windows/Linux in same configuration

Only Physical Standby Same Endianess required on all platforms

Metalink : 413484.1

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More Features: Lost Write Detection

Due to hardware or storage issues lost writes can happen while transmission and blocks may be stale.

Very hard to diagnose in such of case of corruption

Feature:-– Compares version of Blocks

Between Standby blocks and redo stream Version discrepancy can be either standby or primary

– If Primary Database block corruption is detected Resolved Using standby failover and Restore data consistency

New Initialization parameter– ALTER System set db_lost_write_protect = NONE/TYPICAL/FULL– 5% impact but increase protection

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More Features: Automatic Block recovery

11g R2 automatically recovers corrupted blocks from standby copies of blocks

Automatic Block Media Recovery also automatically repair corrupted blocks discovered in the physical standby databases

Reduce recovery time in block corruption cases instead of restoring from tape or disks

RMAN command RECOVER BLOCK can be used for manual recovery and its check for all suitable or consistent blocks across several copies of backups or

– Clause can be added RECOVER BLOCK … EXCLUDE STANDBY then wont check in standby

Automatic block recovery is applicable only in physical corruptions like When checksum is invalid Block contains all zeros Block header is fractured

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More Features: Redo Flush

Yes, Redo can be flushed

Can be done when the primary is in mount mode

To avoid minimal loss of data and allowed failover to be performed without data loss

Syntax:-– ALTER System FLUSH Redo to <target DB Name>

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More Features: Sync with Primary

New command – ALTER SESSION SYNC WITH PRIMARY

– WAIT FOR STANDBY TO BE SYNCHRONIZED WITH PRIMARY– FAILS IF REDO APPLY OR REDO TRANSPORT IS OFF

REPORT TRANSPORT AND APPLY LAGS

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More Features: STANDBY_MAX_DATA_DELAY

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More Features: ROLE Based services

Services can be created and start based on the database ROLE, viz a new addition sys_context (Database ROLE)

In R2 services can be attached via srvctl

Service can failover when using Cluster or Oracle restart

11gR1 to use triggers based on Database role– Example Trigger

role-based-triggers.txt.txt

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Rolling Upgrade : Transient Logical Standby Physical standby must be converted to Logical Standby and uses Flashback

as fall out plan

Downtime for upgrade is only the SWITCHOVER TIME

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Finally, Monitoring Views

GAP_STATUS , additional column in v$archive_dest – GAP or NO GAP

V$dataguard_stats for transport/apply lag

V$REDO_DEST_RESP_HISTOGRAM– Useful when need to analyse network latencies by checking transport lag

V$STANDBY_EVENT_HISTOGRAM

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Thank you!

Q & A