The jobs will remain in PREDWAIT and then REEADY state for a long time. Jobs will eventually run and complete.
The database may be taking a long time to respond to DE (dSeries) updates and selects. Check for following messages in the tracelogs. Normally, wait times should be few seconds to few minutes for most applications. If the wait times are constantly going to over 10-20 minutes to a few hours, then DB is taking a long time to respond.
Release : 12.x
Component : CA WORKLOAD AUTOMATION DE (DSERIES)
If DE has to wait on database then it will take a long time to run the applications and jobs. DE server has to properly update the database in order to trigger the events and run the applications.
Check if there are any issues on the database side, such as a process that is constantly taking up resources in DB server. Backup process should be checked as they sometimes tend to slow the database.