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Do you have to be in a TOR/AOR config to go from CICS v4R1 to CICS TS?

A couple of years ago, while attending an intro to CICS TS session, I seem to recall that one had to be in a TOR/AOR configuration for their CICS/ESA v41 regions. Is this still a requirement for a migration from v4R1 to CICS TS v2.2?

I'm not sure that you got the right message from the dim-and-distant

It is absolutely the case that you do not HAVE to use a TOR/AOR
configuration for CICS - you can quite happily run with everything in a
single region (we do this most of the time in Developing CICS, and I guess
you may well have your own coders who have their own CICS regions).
HOWEVER, in most customer production configurations it is HIGHLY
recommended that you you a TOR/AOR split - and I think the the great
majority of CICS Customers are running with TORs/AORs.

Indeed, with the way CICS is evolving, there will be many TOR-like regions
around talking to loads of AORs (where the real work gets done).

The best way to think of a TOR is a front-end router region for
3270-devices, routing interactive work into an AOR for processing. This
allows lots of different TORs communicating to many back-ends AORs which do
the work. In this way you get an high degree of protection against region
abends as work can automatically be shifted from a failed AOR into an
active one or the terminal can be connected to another TOR to replace a
failed TOR (and a failing TOR is a fairly rare occurance if it's only
processing 3270s). The main benefit of this split is that one can share out
work between AORs and so get best performance for applications.

If you are using CICS' Web Support, you may think it desireable(for
security, performance, reliability reasons etc.) that a distinct region is
used to cope with the HTTP/HTML/IP traffic so keeping this function away
from the AORs which are really doing the work. Thus, you are into having a
sort-of-TOR without 3270s but including TCP/IP to handle communications.

A similar sort of thing applies to use of the CICS Transaction Gateway.
Depending on where the line is drawn between external and internal, the CTG
may communicate with a CICS region that does nothing else apart from route
the request into an AOR

Looking a bit further ahead in CICS TS 2.2, we now have Java facilities
within CICS. Now, a JVM tends to take up more resource running a given set
of activities than an equivalent COBOL/PL1/Assembler program would do.
Therefore, some customers think it desireable to put all java-related work
into AORs that do not have traditional application programs running as
well. This means that the MVS Workload Manager can then control the oomph
given to CICS' Java workload in a different fashion to that given to the
traditional CICS regions.

So, for Production work a TOR/AOR split is vital!

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