Function shipping

Non-System/390® CICS application programs can access resources (data or transactions) owned by a CICS® on System/390 system, and a CICS on System/390 application can access resources owned by a non-System/390 CICS system, in each case provided that the resources are defined as remote in the function shipping system.

A function shipping request takes the form of a normal EXEC CICS command. If either of the following conditions applies, the application-owning system recognizes that function shipping is required and ships the request to the remote resource-owning system.

  1. The EXEC command specifies a remote system in the SYSID option.
  2. The resource is defined as remote.

The mirror program in each CICS product (DFHMIRS in CICS on System/390) handles inbound function shipping.

As already noted, the LU 6.2 protocol is used for all communication between System/390 and non-System/390 CICS systems. Synchronization level 2 on LU 6.2 links is supported by CICS on Open Systems and CICS/400. It is not supported by CICS Transaction Server for Windows. Synchronization level 1 is supported for function shipping between all non-System/390 and System/390 CICS systems. See Syncpointing (LU 6.2).

Restrictions on function shipping

There are some restrictions on function shipping between System/390 and non-System/390 CICS systems.

CICS non-System/390->CICS on System/390

Function shipping the following sequence of commands from a non-System/390 CICS to a CICS on System/390 system causes the System/390 mirror transaction to abend:

DELETEQ TS Q(RFRED)
WRITEQ TS Q(RFRED) FROM()
SYNCPOINT

This is because, on CICS on System/390, you cannot delete a recoverable temporary storage queue and then write to it, without issuing a syncpoint between the two commands.

DL/I database access

Non-System/390 CICS systems cannot function-ship requests to DL/I databases accessed through CICS on System/390 systems. To access DL/I databases from CICS Transaction Server for Windows, CICS on Open Systems, or CICS/400, use distributed transaction processing or the distributed program link function.

Data conversion

CICS Transaction Server for Windows and CICS on Open Systems use ASCII1 data representation and CICS/400 and CICS on System/390 systems use EBCDIC2. When conversion is necessary, the ASCII-based system always converts system data such as resource names. Conversion of user data is performed as necessary in the resource-owning system. For example, for CICS TS for Windows->CICS function shipping, CICS converts the user data (see Table 2). For CICS->CICS TS for Windows function shipping, CICS TS for Windows converts the user data.

Related concepts
Transaction routing
Distributed program link (DPL)
Asynchronous processing
Distributed transaction processing (DTP)
Related reference
Summary of CICS System/390-non-System/390 intercommunication

1.
American National Standard Code for Information Interchange
2.
Extended Binary-Coded Decimal Interchange Code

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