Overriding fixed pacing counts

The pacing counts specified on the LU definition statement apply to all sessions in which the LU participates. Values stated in the APPL definition statement override the values in the logon mode table entry and the LU definition statement. When you specify AUTH=NVPACE, the value for the primary send that goes out in the BIND is 0. Therefore, there is no pacing between the application program and the boundary function.

AUTH=VPACE prevents overloading buffers in the communication controller with outbound messages from VTAM®. You can specify NVPACE when the application program sends a limited amount of data and then waits for a user response.

The primary application program can override the primary receive value for a specific session by specifying a nonzero value in the primary receive field of the session parameters it specifies at OPNDST. If 0 is specified, the primary receive value present in the session parameters in the pending logon is used. Only values less than or equal to the value in the pending logon should be specified by the application program.

Note: NVPACE can also be specified when an application program is sending chains of RUs to a secondary logical unit and the application program cannot send more BIUs than can be held in the queue. The number of elements in each chain must be no larger than the results of the following formula, where n is the smallest value in the VPACING operands of the definition statements for the LUs:

number of elements ≤ 2n - 1

If the application program is in session with LUs whose VPACING operands are different from each other, the smallest VPACING values should be used in the formula.

See Setting initial pacing values for information about how VTAM determines the initial pacing-window size.