Assuming i5/OS, read the Information Center section on Setting up job accounting and the surrounding sections from the navigation pane on the left of that page.
Users may need accounting codes assigned to their profiles. Use CHGUSRPRF ACGCDE(). Or you might assign by job description — CHGJOBD ACGCDE(). And you might modify accounting codes at run time with CHGACGCDE JOB() ACGCDE().
The accounting codes allow for fifteen characters. You might consider planning for, say, the first nine characters to identify individuals. Maybe the first three for the department, the next three for office, the final three for user. Then, as different projects or jobs are started, assign the values to the last six characters.
An individual might be in department 001, office PAY, user 010. A project/job might have WKYCHK as its code, perhaps because it’s a weekly process that calculates checks. (It’s probably best not to put meaning in the codes themselves, so ’012′ or any meaningless string is preferable to ‘WKY’ and ’987′ is better than ‘CHK’.)
When generating accounting reports, you can request info based on subsets/substrings of the accounting codes for logged info. You might request info for all activity relating to ’010′ in positions 7-9 and ‘WKY’ in 10-12 to get all of user ’010′ weekly payroll processing.