Below message found in "alert.log" file when shutdown immediate hung for long time
Thu DEC 19 21:08:00 2015 Active call for process 4448 user 'SYSTEM' program 'ORACLE.EXE (J001)' SHUTDOWN: waiting for active calls to complete.
1. connect to SYS user with new terminal window
SQL> conn / sysdba Connected to idle instance.
2. shutdown database with ABORT option
SQL> shutdown abort; ORACLE instance shut down.
3. open database for normal shutdown with RESTRICT option
SQL> startup restrict ORACLE instance started.
Total System Global Area 167772160 bytes Fixed Size 788496 bytes Variable Size 149682160 bytes Database Buffers 16777216 bytes Redo Buffers 524288 bytes Database mounted. Database opened.
4. now shutdown database with NORMAL option
SQL> shutdown normal; Database closed. Database dismounted. ORACLE instance shut down.