When JCL/JOB terminates abnormally/unsuccessfully, it is called as job abend. It will give some specific abend code for specific reasons.
for example :
1) S322 - Time abend, when sufficient time is not provided to job.
2) SOC7 - Bad data
3) SO13 - Member not found
4) S806 - load module not found
5) S722 - When there is no space to write ouput in sysout.
6) S222 - Cancelled by operator.
7) S522 - SYSOUT filled with display messages and there is no space to write output in SYSOUT area.