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application programs may be placed above the 16 megabyte line if they are
written in VS COBOL II, PL/I, C++ or HLASM.
If you have a need to combine systems or you are adding new CICS applications
that could introduce additional virtual storage constraints, you should consider
the use of CICS Multiple Region Operation (MRO). In addition to providing virtual
storage constraint relief, MRO may provide better utilization of multiple
processors and improved availability and integrity for your CICS/MVS
applications. These benefits are accomplished by the separation of functions
into separate address spaces. Note that MRO path lengths will be longer than for
a single system image, and there are considerations for operations, recovery,
and application design.
A typical MRO system could have one address space for terminal activity (TOR),
one for data base activity (FOR), and one or more for application code (AOR). By
separating these functions, some problems may be isolated to a single address
space (application function). This means that other functions may continue to
operate and the time required to restore a lost function may be reduced.
An example of an MRO environment is depicted in Figure 11:
┌─────────────────────────────────────────────────────┐
││
│ MVS COMMON AREA │
││
├──────────┬──────────┬──────────┬─────────┬──────────┤
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ CICS/OS │ CICS/OS │ CICS/OS │ CICS/OS │
│ ACF/VTAM │ │ │ │ │
│ │TERMINALS │ APPL. 1 │ APPL. 2 │ DATA │
│ │ │ │ │ BASES │
│ │ │ │ │ │
│ │ (TOR) │ (AOR1) │ (AOR2) │ (FOR) │
│ │ │ │ │ │
│ │ │ │ │ │
├──────────┴──────────┴──────────┴─────────┴──────────┤
││
│ MVS │
││
└─────────────────────────────────────────────────────┘
Figure 11. Example of an MVS CICS/OS System using MRO
Note: CICS TS 1.2 also supports VSAM Record Level Sharing (RLS), which may
reduce the need for some FORs.
6.1.5 CICS General System Considerations
As part of the CICS/VSE to CICS TS migration there are release enhancements
you should know about before the migration; below are a few to consider.
CICS TS products no longer support: Macro-level programs, BTAM devices and
controllers, CICS internal security and signon table, Nucleus load table,
Application load table, system generation, journaling to tape, shutdown statistics
136 VSE to OS/390 Migration Workbook