Dg v1 3 ukoug_sg.pptx

Our Awards:
UKOUG Technology Conference 2013
By Marcin Przepiorowski, Senior Oracle DBA
December 2013
Data Guard - Implementation Tips

Marcin Przepiorowski
Oracle Capability Group
Core
Technology
Development
Tools
E-Business
Suite
Business
Intelligence
Java/SOA
About Version 1
Technology Leadership
Architectural Oversight
Knowledge Sharing
Certification and Training
Peer Support and Mentoring
Lessons Learned

About me
Working with Oracle technology since 2001
@pioro
marcin.przepiorowski
oracleprof.blogspot.com

Agenda
• Configuration
• RMAN
• Role Change
• Client connectivity
• Standby database performance
• Monitoring / issues
• Oracle Restart
• Active Data Guard
• Oracle 12c – Far Sync

DataGuard: Configuration
• Database protection mode
– Maximum Performance
– Maximum Availability
– Maximum Protection

• Log transport
– synchronous - since 11g done by child processes spawned by LGWR
– asynchronous - ARCn processes

• NET_TIMEOUT
– SYNC mode only
– Default value 30 sec – LGWR will hang for 30 sec waiting for confirmation
– Recommended value 10 sec

• COMPRESSION
– Support current redo logs (11.2+) and gap resolution
– Additional licence required
– Details ID 729551.1

• MAX_CONNECTIONS
– Default is 1 connection
– Leave the default until you really need to change it – in 11.1 it disable real time apply
– Helping resolve gap (sometimes)

• Listener separation
– Application
– Data Guard
• Static entries for Data Guard Broker services:
– Deafult <db_unique_name>_DGMGRL
– Name can be customized

• Register your application in listeners using “local_listeners”
or static entries
• Use “listener_network” parameter to configure dedicated
network for Data Guard in RAC configuration to avoid
wrong load balancer redirection

• Changes of Data Guard related parameters in Broker
will be pushed into instance parameter file
• Changes of Data Guard related parameters in instance
will be NOT pushed into Broker configuration
• Differences will be reported and some of them can be overwritten
by Broker

• Flashback database
– Required for Fast Start Fail-over
– Re-instance database
– Snapshot database

DataGuard: RMAN
• Create standby using RMAN
– Duplicate from active database – no backup required
12c is using using network backup set from service
– Duplicate from existing backup

• Resolving standby GAPs using RMAN in 11g
– Find oldest SCN applied into standby data files from these two sources
MIN ( CHECKPOINT_CHANGE# ) from V$DATAFILE
CURRENT_SCN from V$DATABASE
DataGuard: RMAN

Primary
backup incremental from scn XXXXXXXXX database format ‘bck_%d_%s…’
backup current control file for standby format ‘control_........’
Standby
catalog start with ‘/…..’
recover database noredo;
Restart instance into nomount
Restore controlfile from ‘/backup/……….’;
DataGuard: RMAN – 11g

Primary
backup current control file for standby format ‘control_........’
Standby
recover database from service <primary> using compressed backupset;
restore control file from ‘/backup/……….’;
restart instance
DataGuard: RMAN - 12c

• Fast switchover
– Make sure listeners are up on standby
– Stop applications listeners on primary
– Check if Primary / Standby are in sync
– Kill all sessions from Oracle / OS
– Switch redo log file on primary database
– Start switchover
DataGuard: Role change

DataGuard: Role change
• Fast failover
– Make sure listeners are up on standby
– Check if Primary / Standby are in sync
– Switch redo log file on primary database
– Shutdown abort primary database
– Failover database using Broker

DataGuard: Client connectivity
• Use services to access database
• Control services with triggers
• Transparent Application Failover can work with Data Guard
– Connection time failover
– Session / Select failover
• Data Guard has support for WebLogic connection pools
• Data Guard has support for ONS / FAN
• DNS alias to connect to primary / standby database

DataGuard: Client connectivity
exec dbms_service.create_service('testrac_taf','testrac_taf');
exec DBMS_SERVICE.START_SERVICE('testrac_taf');
create trigger start_service_trg after startup on database
…
if v_role = 'PRIMARY' then
DBMS_SERVICE.START_SERVICE('testrac_taf');
else
DBMS_SERVICE.STOP_SERVICE('testrac_taf');
end if;
…

DataGuard: Standby database performance
• Standby is just another Oracle database
• Remote Statspack is possible if standby is in open mode
• V$SESSION / V$SYSTEM_EVENT / V$SESSION_EVENT
• Write your own script or find a one working in mount state

• There are two main phases on standby
– Applying logs
– Checkpoints
• Play with number of parallel processes applying logs P0xx
• Make sure all data are in buffer cache
• Check hardware statistics ( CPU / disks / network )
• Consider disabling flashback mode on standby if your disk are overloaded

Problem – standby is behind primary
• Database is switching 2 GB logs once per minute
• 20 sec spend during apply process
• 40 sec spend doing checkpoint on standby
– checkpoint is done after every switch
Solution
• Increase size of redo / standby logs from 2 GB to 19 GB
less time will be spend for checkpoints

DataGuard: Monitoring / Issues
v$dataguard_stats;
v$dataguard_status;
v$recovery_progress;
alert.log, trace files

DataGuard: Monitoring / Issues
• Bounce ARCH process on primary
• Make sure you have same password file on both nodes
• Recreate standby control file
• Delete and recreate broker configuration
• Search for know bugs

DataGuard: Oracle Restart
• If you are not using 11.2.0.4 PSU OCT 2014 be aware of wrong open mode
after fail/switch over if there is no Active Data Guard License in place
Check bug / enhancement request - 9375220 and Note ID 1522542.1
• To avoid manual intervention CRS script can be used
check my blog for details - http://oracleprof.blogspot.ie/2012/08/dataguard-
and-oracle-restart-how-to.html

DataGuard: Active Data Guard
• Standby database is open for read only queries
and log applying is still running in background
• Additional licence but you can use your standby database
for reports
• Queries can wait until standby will be synchronized
and maximum delay when query will run can be defined

DataGuard: Active Data Guard
• With some work (using instead of triggers and db links)
Active Data Guard can be treat like Read Write
• RMAN can use standby to recover corrupted blocks

DataGuard: Oracle 12c – Far Sync
• Synchronous mode for longer distance between primary
and standby

DataGuard: Oracle 12c – Far Sync
DC 1 DC 2
Round trip – 32 ms – SYNC mode increase commit time
5000 km
Round trip – local network – no problems with SYNC and commit time

Q & A
www.version1.com
oracleprof.blogspot.com

Dg v1 3 ukoug_sg.pptx

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