shutdown active processes prevent shutdown operation

When shutdown immediate hanged for long I found in user dump a trace file containing messgaes

ksukia: Attempt 1 to re-kill process OS PID=7427.
ksukia: Attempt 2 to re-kill process OS PID=7427..
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.
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$ ps -ef grep 7427

...

oracle 7426 11402 0 09:34 pts/1 00:00:00 sqlplus @a.sql

oracle 7427 7426 0 09:34 ? 00:00:00 [oracle] defunct

This process 7427 was defunct (dead) as it appeared defunct. So this could not be killed directly with kill -9, instead its parent process sqlplus was killed and shutdown immediate proceeded

Many guys on interent suggested shutdown abort but that must be avoided.