Error: ORA-12537: TNS:connection closed
Details: Occurred on a standby database after switchover from primary to standby. Error came up when checking DataGuard broker configuration.
Cause: The mrp process not running on standby
Solution:
Checked if MRP process was running on standby by executing:
ps -ef | grep mrp
Nothing was running.
Performing regular maintenance on standby database fixed the issue
SQL> SHUTDOWN IMMEDIATE; SQL> STARTUP NOMOUNT; SQL> ALTER DATABASE MOUNT STANDBY DATABASE; SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;