IMS Connect override for the z/OS TCP/IP KeepAlive interval

IMS Connect can override the default KeepAlive interval that is defined in z/OS® for TCP/IP socket connections.

The KeepAlive function, which is a function provided by the TCP/IP protocol, can detect certain socket error conditions by sending a KeepAlive packet on sockets that have been inactive for a specified interval. For example, the KeepAlive function can detect sockets that are no longer valid because the client has abruptly disconnected without informing IMS Connect.

By default, IMS Connect accepts the specification set in the z/OS layer for TCP/IP sockets; however, if a KeepAlive interval set by z/OS is large, as might be the case for installations trying to reduce network traffic, the large interval can delay the detection of an invalid socket by IMS Connect.

To help detect error conditions earlier on IMS Connect sockets, you can specify a smaller KeepAlive interval for IMS Connect ports. Each port defined to IMS Connect can specify a different KeepAlive interval. The KeepAlive interval specified for each port applies to all sockets that use that port.

Typically, a network manager determines if IMS Connect sockets require a different KeepAlive interval from the value defined by z/OS for the TCP/IP stack. After the KeepAlive intervals for IMS Connect are determined, an IMS System Programmer updates either the PORT or DRDAPORT parameters in the IMS Connect HWSCFGxx PROCLIB member with the KeepAlive intervals.

For IMS Connect clients that access IMS TM, KeepAlive intervals can be specified by using the KEEPAV parameter of the PORT keyword in the TCPIP configuration statement in the HWSCFG PROCLIB member.

For IMS Connect clients that access IMS DB, KeepAlive intervals can be specified by using the KEEPAV parameter of the DRDAPORT keyword in the ODACCESS configuration statement in the HWSCFG PROCLIB member.

The range of valid values for the KEEPAV parameter is defined by the TCP/IP protocol and is from 1 to 2 147 460 seconds. A KEEPAV value of zero accepts the KeepAlive interval set in the z/OS layer for the TCP/IP stack. KEEPAV=0 is the default.

You can display the current KeepAlive interval for by issuing any of the following commands:

An IMS Connect-defined KeepAlive interval is not supported by ports defined by using the PORTID parameter, by “LOCAL” ports, or by SSL ports. If the KEEPAV parameter is specified for any of these ports, IMS Connect abends during initialization.