Guidelines for setting DELAY

To select a DELAY operand value, use the following procedure:

During periods of the day when it is most likely that you are experiencing performance problems, turn on the tuning statistics. For channel-to-channel attachments, turn on tuning statistics at each processor using the following operator command:
```
F NET,TNSTAT,CNSL,TIME=1
```
For each recording of the tuning statistics, check the amount of coattailing that is occurring. For channel-to-channel connections, compare the TIMERS and CHNRM values of the channel-attachment major node associated with each host processor. The desirable TIMERS value is 0, but an occasional nonzero value is acceptable.
For channel-to-channel attachments, if the TIMERS value in any tuning statistics record is too large, deactivate the channel-attachment major node at each host processor, and activate a previously defined major node in which DELAY=0 has been specified on the LINE definition statement.
For other channel attachments, if the average number of PIUs seems too high (thereby indicating possible response time problems), you can activate alternate definitions with a lower DELAY value.

The following events cause PIUs on the queue to be sent before the DELAY time elapses:

VTAM® reaches the MAXBFRU limit.
VTAM sends virtual route pacing responses.
VTAM sends transmission priority two traffic.
VTAM reaches the QDPTH value.

The default value for the DELAY operand is 0 (for example, no coattailing). Take the default under the following conditions:

A low rate of transactions that use the channel-to-channel connection. A rate of under five transactions per second is considered low.
Channel-to-channel traffic with frequent bursts of SENDs, such as from an application program that makes inquiries of the other host in rapid succession.

You can also analyze the average number of bytes transferred per I/O operation by dividing the total number of bytes transferred (RDBUF) by the number of READ channel programs (CHNRM).