Scenario 7: Switchover from Source PDB to Target PDB
A switchover exchanges the source and target roles between the specified
PDBs. This is generally a planned role transition, and, because both PDBs are online
and accessible, there is no data loss. Switchovers are useful for load balancing and
to facilitate planned maintenance operations. For the example DG PDB configuration,
a switchover is used to faciliate adding PDB-level standby redo logs for the
bos_sales
PDB at the boston
container
database.
To add PDB-level SRLs to the current source PDB
bos_sales
, this PDB must first be placed in a target role. To
do this, perform a switchover to the target PDB nyc_sales
and then
add PDB-level SRLs to the new standby PDB bos_sales.
DGMGRL> SWITCHOVER TO PLUGGABLE DATABASE nyc_sales AT NEWYORK;
Verifying conditions for Switchover...
Source pluggable database is 'BOS_SALES' at database 'boston'
Performing switchover NOW, please wait...
Closing pluggable database 'BOS_SALES'...
Switching 'BOS_SALES' to standby role...
Waiting for 'NYC_SALES' to recover all redo data...
Stopping recovery at 'NYC_SALES'...
Converting 'NYC_SALES' to primary role...
Opening new primary 'NYC_SALES'...
Waiting for redo data from new primary 'NYC_SALES'...
Starting recovery at new standby 'BOS_SALES'...
Switchover succeeded, new primary is "NYC_SALES"
DGMGRL> SHOW CONFIGURATION;
Configuration - Boston
Protection Mode: MaxPerformance
Members:
boston - Primary database
newyork - Primary database in NewYork configuration
Data Guard for PDB: Enabled in TARGET role
Configuration Status:
SUCCESS (status updated 29 seconds ago)
To create standby redo logs for PDB bos_sales
, first stop redo
apply:
DGMGRL> EDIT PLUGGABLE DATABASE bos_sales AT boston SET STATE='APPLY-OFF';
Succeeded.
Then
connect to the new target CDB boston
as SYSDBA and issue the
following SQL commands to add PDB-level SRLs:
SQL> ALTER SESSION SET CONTAINER=bos_sales;
Session altered.
SQL> ALTER DATABASE ADD STANDBY LOGFILE thread 1
2 group 4 ('$ORACLE_BASE/fast_recovery_area/BOSTON/onlinelog/standby_redo04.log') size 200M,
3 group 5 ('$ORACLE_BASE/fast_recovery_area/BOSTON/onlinelog/standby_redo05.log') size 200M,
4 group 6 ('$ORACLE_BASE/fast_recovery_area/BOSTON/onlinelog/standby_redo06.log') size 200M,
5 group 7 ('$ORACLE_BASE/fast_recovery_area/BOSTON/onlinelog/standby_redo07.log') size 200M;
Database altered.
Use the VALIDATE PLUGGABLE DATABASE
command to confirm successful
creation of the PDB level standby redo logfiles:
DGMGRL> VALIDATE PLUGGABLE DATABASE bos_sales AT boston;
Ready for Switchover: NO
Data Guard Role: Physical Standby
Apply State: Not Running
Standby Redo Log Files: 4
Source: NYC_SALES (con_id 3) at newyork
Finally, use DGMGRL to restart redo apply and check that the DG PDB configuration is
now in a SUCCESS state and no longer lags the source PDB:
DGMGRL> EDIT PLUGGABLE DATABASE bos_sales AT boston SET STATE='APPLY-ON';
Succeeded.
DGMGRL> SHOW CONFIGURATION;
Configuration - Boston
Protection Mode: MaxPerformance
Members:
boston - Primary database
newyork - Primary database in NewYork configuration
Data Guard for PDB: Enabled in TARGET role
Configuration Status: SUCCESS (status updated 58 seconds ago)
DGMGRL> SHOW PLUGGABLE DATABASE bos_sales AT boston;
Pluggable database - BOS_SALES at boston
Data Guard Role: Physical Standby
Con_ID: 3
Source: con_id 3 at newyork
Transport Lag: (unknown)
Apply Lag: (unknown)
Intended State: APPLY-ON
Apply State: Running
Apply Instance: boston
Average Apply Rate: (unknown)
Real Time Query: OFF
Pluggable Database Status:
SUCCESS
Note that target PDB bos_sales
has (unknown)
transport lag and apply lag states. Connect to the source database
newyork
as SYSDBA and archive the current logfile a few times
to initiate redo transport to the newly created standby redo logfiles:
SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;
System altered.
SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;
System altered.
With redo now being shipped to and applied from the standby redo logfiles, the
target PDB will become synchronized with the source
PDB: DGMGRL> SHOW PLUGGABLE DATABASE bos_sales AT boston;
Pluggable database - BOS_SALES at boston
Data Guard Role: Physical Standby
Con_ID: 3
Source: con_id 3 at newyork
Transport Lag: 0 seconds (computed 2 seconds ago)
Apply Lag: 0 seconds (computed 2 seconds ago)
Intended State: APPLY-ON
Apply State: Running
Apply Instance: boston
Average Apply Rate: 27 KByte/s
Real Time Query: OFF
Pluggable Database Status:
SUCCESS