Overview of when the LISTBC exits receive control

The LISTBC exits receive control when users issue the LISTBC command and when users log on to TSO/E (during logon, LISTBC processes mail and notices).

The initialization exit receives control before LISTBC invokes the parse service routine to parse the command. The exit gets control if you are using user logs or the broadcast data set to store messages, that is, the value of EESCB_LOGNAME is either * (indicating the name of the current broadcast data set) or a user log name.
When a user logs on, the initialization exit receives control before LISTBC opens the broadcast data set or the user log to retrieve messages.

After the initialization exit returns control to LISTBC, LISTBC determines whether it should process notices. If so, LISTBC retrieves any notices from the broadcast data set.

LISTBC then determines whether it should process mail. If not, LISTBC invokes the termination exit and then completes processing. If so, LISTBC determines whether it retrieves mail from the broadcast data set or the user log. The LISTBC command processor then continues processing and invokes the appropriate exits as described below.
The pre-list exit receives control only if EESCB_LOGNAME in the copy of the control block is a user log name. The exit receives control before LISTBC associates (allocates) the user log data set name to a ddname and opens the user log data set.
The pre-allocate exit receives control if both of the following are true:
- EESCB_LOGNAME in the copy of the control block is a user log name
- The user's user log data set does not yet exist
LISTBC tries to associate (allocate) the user log data set name to a ddname. If the allocation fails because the user log does not exist, LISTBC invokes the pre-allocate exit. If the allocation is successful, the user log exists and the pre-allocate exit does not receive control.
The pre-read exit receives control only if EESCB_LOGNAME in the copy of the control block is a user log name. The exit receives control:
- After LISTBC opens the user log data set
- Before LISTBC reads a message
The pre-read exit gets control for each message in the user log.
The pre-display exit receives control only if EESCB_LOGNAME in the copy of the control block is a user log name. The exit receives control before LISTBC displays the message to the user.
The pre-display exit gets control for each message in the user log. After LISTBC reads and displays all of the messages, it closes the data set.
The failure exit receives control only if EESCB_LOGNAME in the copy of the control block is a user log name. The exit receives control whenever LISTBC detects an I/O error on the user log when it is opening or closing the data set, or retrieving a message.
The termination exit receives control just before LISTBC completes processing. The exit gets control if you are using user logs or the broadcast data set to store messages, that is, the value of EESCB_LOGNAME is either * (indicating the name of the current broadcast data set) or a user log name.