The first 4 passwords in password history are kept in the logonid record. If extended password history is used, going from 5 to 64 passwords can be kept, will cause ACF2 to create a password profile record for each user.
The User Password Profile record is broken into three parts. The first two parts are static: x'6E' and x'9C' in length, or x'10A'. Once defined these do not change. Each password remembered takes up x'11' bytes. So, the fifth password change will cause a User Password Profile record to be generated on the INFOSTG database for a x'11B' in length and so on, for example:
5 passwords x'11B'
6 passwords x'12C'
7 passwords x'13D' and so on.
These records are "trimmed" and VSAM takes care of it when the length increases. After implementing password history, keep an eye on the FREESPAC, and splits to the VSAM files. You may need to do a REORG or even increase the database size depending on the amount of users you have on the system.