Remote resources that can be accessed

Function shipping requests can access the following remote resources:

CICS file control data sets

Function shipping allows access to files located on a remote CICS system. The following EXEC CICS commands are not supported:

Both read-only and update requests are allowed. Protection of data depends on the security facilities available to the different CICS products. Updates to remote recoverable files are not committed until the application program issues a syncpoint request or terminates successfully. Logically-related updates of local and remote files can be performed within the same logical unit of work, even if the remote files are located on more than one connected CICS system.

Care should be taken when designing systems that use remote file requests containing physical record identifier values (examples include BDAM, VSAM RBA, and files with keys not embedded in the record). Application programs in remote systems must have access to the correct values following updating or reorganization of such files.

IMS databases

Function shipping allows a CICS on System/390 transaction to access IMS/ESA® DM and IMS/VS DB databases associated with a remote CICS OS/390 system, or DL/I for VSE/ESA databases associated with a remote CICS/VSE system.

CICS Transaction Server for Windows, CICS/400, and CICS on Open Systems systems cannot access IMS or DL/I databases by function shipping, but can do so by distributed program link (see Distributed program link). The following discussion applies to CICS on System/390 systems only.

The IMS/ESA DM (DL/I) database associated with a remote CICS system can be a local database owned by the remote system, or a database accessed using IMS database control (DBCTL). To the CICS system that is doing the function shipping, this database is simply remote.

As with file control, updates to remote DL/I databases are not committed until the application reaches a syncpoint. In IMS/ESA DM, it is not possible to schedule more than one PSB for a single logical unit of work, even when the PSBs are defined to be on different remote systems. For this reason, logically-related DL/I updates on different systems cannot be made in a single logical unit of work.

The PSB directory list (PDIR or DLZACT) is used to define a PSB as being on a remote system. The remote system owns the database and the associated PCB definitions. When DL/I access requests are made to another processor system by a CICS system but no local requests are made, it is not necessary to install IMS on the requesting system.

Temporary storage and transient data

Many of the uses made of transient data and temporary storage queues in a single CICS system can be extended to an interconnected system environment. For example, a queue of records can be created in a remote system for processing overnight. Queues also provide a means of handling responses from remote systems, while keeping local terminals free to enter other requests. A response can be returned to a terminal when it is ready, and delivered to the operator when there is a lull in entering transactions.

Temporary storage

Function shipping enables application programs to send data to, or retrieve data from, temporary storage queues located on remote systems. A recoverable queue must be defined as recoverable in its local (resource-owning) system.

Transient data

An application program can access intrapartition or extrapartition transient data queues on remote systems. The resource definition in the requesting system defines the named queue as being on the remote system. The queue definition in the remote system specifies whether the queue is recoverable, and whether it has a trigger level and associated terminal.

If a transient data destination has an associated transaction, the named transaction must be defined to execute in the system owning the queue; it cannot be defined as remote. If a terminal is associated with the transaction, it can be connected to another CICS system and used through the transaction routing facility of CICS.

The remote naming capability enables a program to send data to the CICS service destinations, such as CSMT, in both local and remote systems.

Related concepts
Introduction to function shipping
Transparency to application
How function shipping works
Synchronization
Function shipping examples
Related reference
CICS product communication support
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