Many sites prefer not to use Unix Process Accounting as it represents another item to housekeep. At its worst it's a filesystem filler, which constantly needs to be checked, but at best of course, it's a serious provider of user and command information. Introducing the following into the root crontab should prevent the need to constantly check the size of the output pacct file:

50 23 * * * /usr/lib/acct/accton

52 23 * * * > /usr/adm/pacct

54 23 * * * /usr/lib/acct/accton /usr/adm/pacct

Substitute the relevant paths and times where necessary AND bear in mind that Process Accounting writes its records on process termination, so try to zero the file when applications you want to record have shut down.