There are a few ways to clean up, or remove jobs from job log pending. You can end the job with a value of 0 for the Maximum log entries (LOGLMT) parameter. If the job is already ended, you can run the Remove Pending Job Log (QWTRMVJL) API. You can also use the Work with Job Logs (WRKJOBLOG) command.
To end a job with LOGMLT set to 0, use iSeries™ Navigator or the character-based interface.