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User Exit Reference › Execution Order of User Exits

Execution Order of User Exits

You can decide which user exits can best satisfy the needs of your site by determining at what point in a request CA VM:Tape calls each user exit, and what information is passed to it. The order in which CA VM:Tape calls the user exits for a mount request is described in the following steps.

  1. The user sends a mount request to CA VM:Tape. If the request came over TCP/IP it is authorized by the TCPAUTH user exit.
  2. CA VM:Tape passes the command to the USERCMND or COMMAND exit, which modifies, accepts, or rejects the command.
  3. CA VM:Tape parses the command and checks the syntax.
  4. CA VM:Tape verifies the requested volser with the TMC.
  5. If the mount is for a foreign mount, CA VM:Tape calls the USREXIT1 exit. If CA VM:Tape does not cancel the mount, CA VM:Tape checks the authorizations.

    Note:  If USREXIT1 is called, USREXIT2 is skipped. Also, the CA VM:Secure Rules facility can prevent this exit from being called.

  6. If the mount is not a foreign mount, CA VM:Tape calls the USREXIT2 exit to modify, accept, or reject the mount request.

    Note:  A return code of 4 from the USREXIT2 exit indicates that CA VM:Tape skips the normal authorization checking, as shown in step 7.

  7. CA VM:Tape checks the authorizations; then it calls the USERSECR exit. (The USERSECR exit supersedes the USREXIT2 exit, and is the preferred exit to use for security checking.)
  8. After the authorizations are validated, CA VM:Tape starts the drive allocation process.
  9. CA VM:Tape calls the ALLOCATE exit to modify the EDL.
  10. After CA VM:Tape gets a tape drive and the real device address is known as it calls USREXIT9. Then it sends the operator a message to mount the tape.
  11. After the tape is mounted, but before the label is verified, CA VM:Tape calls the USREXIT3 exit.
  12. CA VM:Tape checks the label, unless the USREXIT3 exit specifies bypass label processing.
  13. CA VM:Tape updates the TMC record and then calls the USERACNT exit, followed by the USREXIT5 exit.
  14. If needed, CA VM:Tape writes a label on the tape.
  15. Before the tape is attached to the user, CA VM:Tape calls the USREXIT7 exit to position the tape after the label.
  16. After the tape drive is detached from CA VM:Tape and attached to the user, CA VM:Tape calls the USREXIT4 exit to create a CP accounting record.