A new run unit would exceed the MAXERUS (maximum external run-units) value, as specified in the SYSGEN.
The following possible causes, you can do.
1. This means the system is very busy now (or having sever problems like example given in third point ) and you should be able to just re-run the job again in a few minutes.
2. Or you can get the help from DBA
i.e. The DBA’s may need to change MAXERUS (maximum
external run units) in the SYSGEN.
3. Other than an abnormally busy system, here is an example that can cause the system to be “busy”. You have a batch job
running in protected update. Online transactions are trying to access the same area, so they go into a WAIT state (up to the number of seconds specified in the external wait time). So instead of finishing in 1 or 2 seconds, the stay in a WAIT state for 1 to 20 minutes. New transactions come in, and they try to access the area, and go into a wait state. So in a matter of minutes, you have 70 online tasks all active - but in a WAIT
state. If your MAXERUS is set to 70 - you have reached it - and all new income transactions will ABEND with a 1473.