You can either directly delete the jobs that you want to using a blcli or a script. Or rather use the cleanup utility. Check the users guide for the same. You can specify the retention period as well and delete the stuff that you dont want.
https://kb.bmc.com/infocenter/index?page=content&id=S%3AKA328042&actp=search&viewlocale=en_US&searchid=1336978235264 talks about how to delete a provisioning job.
https://communities.bmc.com/communities/message/123730#123730 >> this should help you the most.
Thanks a lot!!!
It was a great help!!!
i didn't follow all the links but the ability to remove job runs is built in as prabhat mentioned. you set the RESULT_RETENTION property and you enable the retention policy enforcement in blasadmin. then run the Delete executeRetentionPolicy command... that will remove Job Runs.