PROGRAMMING COBOL APPLICATIONS WITHOUT
ITEM: RTA000046727
QUESTION:
My customer plans to develop character-based COBOL applications to run
in a multi-user AIX environment. From a transaction processing point of
view, the customer is asking what products are required to build these
applications.
They will be database applications, using DB2/6000 and MF COBOL. I have
indicated to the customer that these products would be all that is
required to build multi-user applications on a single system image. We
had a high level discussion about the COBOL external file handler, its
embedded SQL support, and the DB2/6000 support for 2 phase commit. But
my customer is still not confident that he has everything he needs to
build these applications.
He asks, "What transaction monitor is doing the CICS-like work that
occurs in a legacy CICS/MVS environment? Terminal and printer control?
If I don't have CICS/6000 how do I do it?"
We also discussed the CICS/6000 products, but I indicated that unless
this will become a distributed OLTP application, there may not be any
advantages to have the CICS products, especially when programming in
COBOL.
Could you please offer discussion about how COBOL and DB2/6000 work
together in developing on-line applications? Please mention how things
compare to CICS environment and why/why not CICS would be an advantage?
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A: If you create a multi-user application without using CICS/6000 then
each occurrence of a user invoking the application will run in a separate
process. You will want to use the Micro Focus Cobol options for linking
the application such that the code is brought into memory once, and
each user shares that executable. In this environment there is no
transaction manager that terminates your transaction when you are
inactive. Your working storage stays in memory during your think/respond
time. If the system memory is overcommited, the AIX operating system
will swap inactive user's working storage to the paging space to free
up memory pages for the active users. Since everyone is accessing the
executable, it will not get paged out. DB2 sees each of these users
separately and spawns an agent for each of them to communicate with DB2.
Applications generating print requests will use the AIX print queueing
backed to handle these print requests.
The advantage of this approach is it makes application design
and coding simpler. This is the "normal" programming method for
most unix applications. The downside is this method causes more
system overhead (lots of processes for AIX to manage) and results
in the need for larger machines and more memory.
Applications coded to a transaction manager like CICS/6000 or
Top-End, Tuxedo, or Encina Monitor cause the users to share resources
by having users serviced by multi-threaded application code running
in a shared process. The monitor opens a restricted number of these
processes and gives the administrator more control of how many processes
are kept open for what kinds of work. This provides a level of
application load balancing the customer is used to on the mainframe.
The downside is the need to install and maintain a more complex
operating environment including DCE, Encina, and the CICS lpp's.
This method is encouraged when you need to service a very large
number of users, and the application has well defined, predictable
queries that can be canned. It is also recommended where there are
large amounts of think time between transactions. This method frees
up system resources from the user during that think time.
These advantages/disadvantages are roughly the same as the customer
is used to in choosing application design on the mainframe. The
CICS/6000 environment is comparable to what they are used to in CICS/MVS.
The alternative method (without CICS) is more comparable to the
mainframe CMS environment.
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This item was created from library item Q668481 CVDFS
Additional search words:
ADVANTAGES APPLICATION APPLICATIONS CICS CICS6000 COBOL COMPILERS
CVDFS DISADVANTAGE IX LANGUAGE OZNEW PROGRAMMING RISCL RISCSYSTEM
SEP94 SOFTWARE 6000
WWQA: ITEM: RTA000046727 ITEM: RTA000046727
Dated: 06/1996 Category: RISCL
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