HOT I/O session termination

Using the HOTIOTRM start option, you can set the threshold at which VTAM® will terminate "hot" (out-of-control) sessions. HOTIOTRM specifies the percentage (10–99) of the current size of the I/O buffer pool that a single session must have allocated to it to cause VTAM to take corrective action. If HOTIOTRM is allowed to default to 0, VTAM will not terminate sessions based on I/O buffer pool usage.

If HOTIOTRM is specified with a value in the range 10–99, and 1 or more sessions have been identified by VTAM as using a percentage of the I/O buffer pool greater than or equal to that value, VTAM will then attempt to stop the buffer pool expansion with one of the following actions:

Deactivate the LU when the session type is SSCP-LU.
Deactivate the PU when the session type is SSCP-PU.
Terminate all sessions between the two logical units when the session type is LU-LU.

The above action will be taken if all of the following criteria are met:

The percentage of the pool in use by the session is greater than or equal to the HOT I/O session termination threshold as specified by the HOTIOTRM start option.
The subarea of one or both session partners must be the subarea in which the HOT I/O is being detected.
When the session type is SSCP-PU, the PU is not an NCP.

If all of the above conditions are true and it is an LU-LU session, VTAM terminates all sessions between the two session partners. It then issues message IST1099I, indicating that the sessions have been terminated.

If all of the above conditions are true and it is a SSCP-LU or SSCP-PU session, VTAM deactivates the LU or PU. It then issues message IST1098I, indicating that the LU or PU has been deactivated.