11g Dataguard Enhancements

8/11/2019 11g Dataguard Enhancements

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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 & DisasterRecovery Solution


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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 2New

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 instandby mount

mode

Open readonly

Open modechanged to read

only

Start the redoapply again using

log file (SRLs)

Status changed toread only apply


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Turn on Physical Standby to Snapshot StandbyOnce sync check,

convert standby tosnapshot

Open database

Read writemode

Need to closedatabase

Switched back tophysical standby


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Additional InfoActive / Snapshot

WHAT OPERATION ALLOWED IN ACTIVE

DATA GUARD ?SELECT statementsComplex queriesCalling of stored proceduresUse of database links to redirect DML to

PrimaryUse of stored procedures to call remotestored procedures via database linksUse of SET ROLEUse of ALTER SESSION and ALTERSYSTEMNo Datatypes restrictions like LogicalStandby

Additional TEMPFILES can be created forSortsFlashback Query : SELECT AS OFAdditional License

SOME IMPORTANT POINTS FOR SNAPSHOTSTANDBY DATABASE

PHYSICAL STANDBY DATABASE SHOULD BE INFLASHBACK MODE

NO REAL TIME QUERY OR DATA NO FAST START FAILOVER IN THIS MODE

NO SWITCHOVER/FAILOVER UNTILCONVERTED TO PHYSICAL STANDBY

Free of Licence POINTS

1. Configure the Flash Recovery Area2. Set the Retention Target

3. Enable Flashback Database


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10g Equivalent Snapshot commandsPrepare the physical standby database to be activated

SQL> 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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DATGUARDStill More Features


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More FeaturesRMAN Active database Duplication

RMAN> run {

allocate channel prmy1 type disk;




allocate auxiliary channel repstby type

disk;

duplicate target database for standby from

active databasespfile

parameter_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


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More FeaturesRedo 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 FeaturesHeterogenous database support

} Oracle 10g Dataguard support mixed environments 32bit and 64 bitconfiguration

} Oracle 11G Dataguard supports mixed Windows/Linux in sameconfiguration

} 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 transmissionand 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 ofblocks

} Automatic Block Media Recovery also automatically repair corrupted blocksdiscovered 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 andits check for all suitable or consistent blocks across several copies ofbackups 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


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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 OFFREPORT 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 newaddition 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


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

as fall out planDowntime for upgrade is only the SWITCHOVER TIME


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Finally, Monitoring Views

} GAP_STATUS , additional column in v$archive_destGAP or NOGAP

} 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

11g Dataguard Enhancements

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