No work processes are available for &1 background jobs

What causes this issue?

According to the settings for parallel processing, more background jobs
are supposed to run in parallel than there are background work
processes available in the current configuration of the servers.

System Response

The system will reduce the number of jobs to be scheduled to the number
of available background processes.

How to fix this error?

Check your server configuration or your settings for parallel
processing.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.