Accessing external systems from within IMS

IMS™ application programs can access external systems to use data that resides in those external system or to interact with business logic that resides outside of the IMS environment.

IMS application programs that want to use external subsystem data can use either or both of the following facilities:

The External Subsystem Attach Facility (ESAF), which can be used by JMP, JBP, MPP, BMP, and IFP application programs, can access external subsystem data, such as Db2 for z/OS® databases or IBM® MQ
The DB2® Recoverable Resource Manager Services Attach Facility (DB2RRMS), which can be used by JMP and JBP applications that access Db2 for z/OS databases

You can specify both ESAF and DB2RRMS access in one SSM PROCLIB member.

IMS application programs that want to interact with business logic that resides outside of the IMS environment can do so using the IMS callout function. The callout requests can be either synchronous or asynchronous. The target of the callout request can be:

Any generic web service, after going through IMS Enterprise Suite SOAP Gateway.
A message-driven bean, an Enterprise JavaBeans component, a Java™ EE application, or web service, after going through IMS TM Resource Adapter.
A user-written IMS Connect TCP/IP application or a vendor-supplied solution that uses TCP/IP and the IMS Connect protocol to retrieve callout requests.

Related reading:

For more information about installing and defining external subsystems to IMS, see:
- Accessing multiple external subsystems in IMS Version 13 Communications and Connections.
- Specifying the SSM= EXEC parameter in IMS Version 13 System Definition.
For more information about the software requirements of the callout function, see IMS Version 13 Release Planning. For more information about how application programs can use the callout function, see IMS Version 13 Application Programming.