Clearly OMS and OEM are connected (Oracle Enterprise Manager Grid Control or DBConsole) via users SYSMAN and DBSNMP.
These sessions should be de-activated (that is to log off any OEM, OMS, SYSMAN and DBSNMP) before the shutdown immediate is attempted.
Oracle Enterprise Manager, Grid Control, Dbconsole and agents keep doing internal processing.
This may include a few PLSQL notification procedures running on the database by database control like
BEGIN EMD_NOTIFICATION.QUEUE_READY(:1, :2, :3); END;
As per internal documentation of the shutdown immediate, if there are active calls then it would wait for all the active calls to finish.
To implement the solution:
1. Given OEM connections are active (SYSMAN and DBSNMP), de-activate these sessions, i.e. by stopping the agent/DBConsole
2. Then shutdown immediate as normal
- OR -
There may be processes still running and holding locks at the time a shutdown is issued.
Sometimes these are failed jobs or transactions, which are effectively 'zombies', which are not able to receive a signal from Oracle.
If this occurs, the only way to shutdown the database is by doing:
sql>
shutdown abort
startup restrict
shutdown normal
The startup does any necessary recovery and cleanup, so that a valid cold backup can be taken afterward.
If this issue occurs frequently, it would be a good practice to see if there are any active user processes running in v$session or v$process before shutting down the instance.
If the problem persists, and no apparent user processes are active, you can set this event prior to issuing the shutdown command in order to see what is happening. This will dump a systemstate every 5 minutes while shutdown is hanging
SQL>
connect / as sysdba
alter session set events '10400 trace name context forever, level 1';
Then issue the shutdown command.
3. You can kill the sessions preventing shutdown. Refer: Alert Log: Shutdown Waiting for Active Calls to Complete (Doc ID 1039389.6)