PeopleSoft encrypts the access ID when it is stored in the PeopleTools security tables. Consequently, an encrypted value can’t be readily referenced or accessed. So when the access ID, which is stored in PSACCESSPRFL, must be retrieved or referenced, the query selects the appropriate access ID by using the symbolic ID as a search key.
The symbolic ID acts as an intermediary entity between the user ID and the access ID. All the user IDs are associated with a symbolic ID, which in turn is associated with an access ID.
If you change the access ID, you need to update only the reference of the access ID to the symbolic ID in the PSACCESSPRFL table. You do not need to update every user profile in the PSOPRDEFN table.