ORA-24324: service handle not initialized

Error: ORA-24324: service handle not initialized

Details: This error occurs when starting up the database by executing STARTUP NOMOUNT or STARTUP MOUNT from SQL*Plus

Cause: Occurs when you try to startup from the same SQL*Plus session you did the shutdown from

Solution:Exit and re-enter SQL*Plus after shutdown and before executing startup again.

Oracle Data Guard 11G: Steps to switch Primary to Standby

Analyzing physical RAM on the server to determine whether an increase needed

Check the total physical RAm on the server by running

lsattr -El sys0 -a realmem

Result would look something like this:

> lsattr -El sys0 -a realmem
realmem 25165824 Amount of usable physical memory in Kbytes False

The go through each end every database running on the server and do the following steps:

1. Login to sqlplus
2. Check MEMORY_TARGET parameter:

   SQL>SHOW PARAMETER MEMORY_TARGET
   

   If value is not 0, then use it, but if it is 0, then use sum of values of SGA and PGA

   SQL>SHOW PARAMETER SGA_TARGET
   

   and

   SQL>SHOW PARAMETER PGA_AGGREGATE_TARGET
   

3. After adding up all the values for each and every running database, calculate the percentage currently taken up. If it is no more than 50-70%, no change needed.

Oracle DataGuard switchiver vs. failover

Switchover is a planned role reversal between primary and standby databases in DataGuard configuration. it guarantees no data loss and is typically done for maintenance. There is no need to re-enable either database when the transition occurs.

Failover is not planned and is typically performed in event of primary database failure event, when there is no possibility of recovering primary database in a timely fashion. When failure occurs, standby database is taking over the primary role. Failover may result in data loss, depending on the protection mode enabled at the time failover occurs.

If a DataGuard broker is enabled, we can automate the failover, however if DataGuard broker is not enabled, we will have to perform manual failover.

If a DataGuard broker cannot detect the heartbeat of the primary DB, it will automatically perform the failover.