We have seen overview and prerequisites of fast-start failover in the previous post.
Steps to configure fast start fail over .
Step 1 : Connect to dgmgrl and check the configuration
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production
Copyright (c) 2000, 2009, Oracle. All rights reserved.
Welcome to DGMGRL, type "help" for information.
DGMGRL> connect sys/oracle
Connected.
DGMGRL> show configuration;
Configuration - dgconfig1
Protection Mode: MaxPerformance
Databases:
testdb - Primary database
std_testdb - Physical standby database
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS
Step 2 : set faststartfailovertarget property.
DGMGRL> EDIT DATABASE TESTDB SET PROPERTY FASTSTARTFAILOVERTARGET=STD_TESTDB; Property "faststartfailovertarget" updated DGMGRL> EDIT DATABASE STD_TESTDB SET PROPERTY FASTSTARTFAILOVERTARGET=TESTDB; Property "faststartfailovertarget" updated
Step 3 : set protection mode if not already set using below syntax.
DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MaxAvailability;
Step 4: a set threshold value for fast-start failover
DGMGRL> edit configuration set property faststartfailoverthreshold=300; Property "faststartfailoverthreshold" updated
Default value is 30 seconds.
Step 5 : Setting the LAG limit parameter.
As in my configuration Protection mode is Maximum Performance. I need to set FastStartFailoverLagLimit. Oracle data guard use this property as an acceptable lag-time limit in seconds. If standby database’s applied redo time exceeds this limit fast start failover is allowed.
Default value is 30 seconds , minimum value is 10 seconds.
Note : This parameter is ignored in Maximum Availibility mode.
DGMGRL> edit configuration set property faststartfailoverlaglimit=50; Property "faststartfailoverlaglimit" updated
The maximum performance failover target must be within the specified lag limit of the primary database for the failover to be allowed. If the failover target is more than the specified lag limit behind the primary database, an error is returned.
Step 6: Set property FastStartFailoverPmyShutdown .
Default value is true. If you do not want to shut down Primary database database after fast start failover is triggered as result of primary redo generation is stalled or primary database loosing connectivity with target standby and observer for more than the time specified by faststartfailoverthreshold then we need to set it to false.
A value of TRUE causes the primary database to shut down with the ABORT option after the elapse of the number of seconds specified in the FASTSTARTFAILOVERTHRESHOLD property.
Step 7: Automatic reinstatement of database
DGMGRL> EDIT CONFIGURATION SET PROPERTY FASTSTARTFAILOVERAUTOREINSTATE=TRUE; Property "faststartfailoverautoreinstate" updated
Step 8: Start observer
[oracle@localhost oradata]$ dgmgrl DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production Copyright (c) 2000, 2009, Oracle. All rights reserved. Welcome to DGMGRL, type "help" for information. DGMGRL> connect sys/oracle@testdb Connected. DGMGRL> DGMGRL> DGMGRL> start observer; Observer started
Step 9: Enable fast_start failover.
DGMGRL> enable fast_start failover; Enabled.
Alert log when we enable Fast_Start Failover :
Fast-Start Failover (FSFO) has been enabled between: Primary = "testdb" Standby = "std_testdb" Sat Jun 23 15:49:22 2018 FSFP started with pid=69, OS id=17552
Viewing Fast_start Failover.
DGMGRL> show fast_start failover;
Fast-Start Failover: ENABLED
Threshold: 50 seconds
Target: std_testdb
Observer: test1.localdomain
Lag Limit: 50 seconds (not in use)
Shutdown Primary: TRUE
Auto-reinstate: TRUE
Observer Reconnect: (none)
Observer Override: FALSE
Configurable Failover Conditions
Health Conditions:
Corrupted Controlfile YES
Corrupted Dictionary YES
Inaccessible Logfile NO
Stuck Archiver NO
Datafile Offline YES
Oracle Error Conditions:
(none)
We can check fast_start failover configuration from the v$database view.
SQL> SELECT fs_failover_status as STATUS,fs_failover_current_target as CURR_TGET, fs_failover_threshold as THRESHOLD,fs_failover_observer_present as OBS_PRES, fs_failover_observer_host as OBS_HOST FROM v$database; STATUS CURR_TGET THRESHOLD OBS_PRE OBS_HOST ---------------------- ------------------------------ ---------- ------- ---------------- SYNCHRONIZED std_testdb 50 YES test1.localdomain
We can see here fast_start failover status is synchronized. We can check status, current standby target, threshold value, an observer is present or not and from which host observer is running.
Stay tuned for More articles on Oracle DataGuard
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