[]$ db2
DB21015E The Command Line Processor backend process request queue or input
queue was not created within the timeout period.
[]$ exit
logout

No user apart from the instance owner is able to login to the database. Get the above error.

However, previously, was able to access the database as other users also.

Any idea?

TIA

Stop the instance and do an instance update db2iupdt ..

HTH

Sathyaram