I started to see the following entries in the /var/adm/cron/log file recently.

Thu Mar 29 11:15:00 EETDT 2012
! cron: 0481-087 The c queue maximum run limit has been reached.
Thu Mar 29 11:15:00 EETDT 2012
! 0481-095 The cron job is being rescheduled.

 

By default on AIX, the cron daemon is only allowed to run 100 concurrent jobs. Under normal conditions, this is probably ok, but in my case, a user had created a cron job that spawned every 5 minutes and due to a stale NFS mount, the script hung, and very soon cron stopped scheduling new jobs.

Upon investigation, I found that you can tune the number of jobs that cron is allowed to concurrently schedule by editing the following file:

/var/adm/cron/queuedefs

 

Adding an entry like this:

c.200j20n60w

 

This means that cron can schedule 200 concurrent jobs with a nice value of 20 and a wait time of 60 seconds till next execution attempt in the case of the limit being reached. You will have to stop (kill 15) the cron process and wait for cron to respawn for the change to take effect.