The system file is the highest-level file in the D3 file hierarchy.
The system file or MDS contains the file-pointers to every account in the database. Entries in the system file define user master dictionaries. The master dictionary pointers are either D-pointers (file definition) or Q-pointers (file synonym). The item-IDs of such items are the user names that the user enters when the system prompts the user to logon. Such items are created with the create-account command.
The system file always includes these standard accounts:
|SQL||The SQL account should never be modified manually (for example, running a sel-restore or account-restore from an older tape). Otherwise, some SQL tables may become inaccessible. Also, because the SQL account is now in the FSI, restoring the VME from an old tape or from the original data set, brings an SQL account inside the VME. If it becomes necessary to restore the VME in this manner, delete this VME SQL account with the delete-account command and then run the QS.UPD utility again.|
|SYSPROG or DM||Contains the system-level files and utilities for use by system managers.|
These accounts contain the initial files used in the maintenance and operation of the system, and they are the only accounts needed to maintain the system.