Path length and resource definition tradeoffs

If more than one System/390® CICS system is communicating with an ASCII system--that is, with CICS® Transaction Server for Windows or CICS on Open Systems--direct and indirect links are possible. The links used affect resource definition effort and processing workload. The processing workload includes data transfer and data conversion.

Where user data conversion is performed by the System/390, it occurs at the first System/390 system for data inbound from the ASCII system, and at the last System/390 system for data outbound to the ASCII system. In Figure 1, an ASCII system running CICS Transaction Server for Windows is linked to two CICS on System/390 systems, directly to CICS1 and indirectly, through CICS1, to CICS2. CICS1 and CICS2 can be connected in any way supported for the particular products. Whatever the connection between CICS1 and CICS2, CICS1 does the conversion for data transferred in either direction.

Figure 1. Where data conversion takes place
Where data conversion takes place

Figure 2 shows an ASCII system, CICS Transaction Server for Windows or CICS on Open Systems, and four CICS System/390 systems. This figure is the basis of the discussion in the rest of this chapter.

The CICS on System/390 systems comprise:

The ASCII system can have a separate LU 6.2 link to each System/390 system. Figure 2 shows three such links: link X to TOR, link Y to AOR1, and link Z to DOR.

Assumptions

Under Possible approaches, the following assumptions are made about Figure 2.

  1. A user of the ASCII system can enter a transaction (TRN1) owned by system AOR1 that requires access to:
  2. Function shipping can take place from the ASCII system directly to TOR, AOR1, and DOR, and indirectly to AOR2.
Note:
Some or all of these requests may require data conversion.

Possible approaches

With the setup in Figure 2, and the stated assumptions, various scenarios are possible, as discussed below.

Note:
In the discussion, the term "data conversion modules" refers to:
  1. The standard data conversion program
  2. The data conversion table
  3. The user-replaceable data conversion program.
All three of these items are required for function shipping and DPL, but only the first two for transaction routing.

Transaction routing: ASCII--TOR--AOR1

The following definitions are necessary:

The ASCII system uses its system services to perform the data conversion from ASCII to EBCDIC.

Transaction routing: ASCII--AOR1

The same resource definitions are required as for transaction routing through TOR (see above), except that:

Function shipping: ASCII--TOR--AOR1--DOR

The following definitions are necessary:

The data conversion modules need to be defined in only one system, TOR, which does the ASCII<->EBCDIC conversion on the transmitted user data.

Function shipping: ASCII--AOR1--DOR

The same resource definitions are required as for the previous example, except that:

Function shipping: ASCII--AOR1 and ASCII--DOR

The same resource definitions are required as for the previous example, except that:

Summary

A direct link from the workstation to the target CICS system gives the shortest path length. If you have several target CICS on System/390 systems, you can ship all requests through a single system in which you have defined the data conversion modules. This enables you to define the data conversion modules in only one place, at the expense of a longer path length and the need to create more remote resource definitions.

Related concepts
Syncpointing (LU 6.2)
Overview of CICS System/390-non-System/390 intercommunication
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