VTAM® has functions to both detect and terminate sessions deemed to be using excessive amounts of the I/O buffer pool. The I/O buffer pool is the storage pool that contains session data. Typically, these sessions are undergoing some sort of malfunction causing an unrestrained transmission of data into VTAM. A failure of VTAM to detect and terminate these out-of-control sessions can result in a VTAM or system outage because of CSA exhaustion. These sessions are commonly referred to as HOT or HOT I/O.