Addressing OLTP Solutions with CICS: The Transaction Server ... - Ibm

3.4.8 Data Location
44 CICS for AIX as the Transaction Server
are not always clearly defined. It is a case of looking at all of the options and
choosing the best one for your environment.
3.4.7.2 Transaction Routing
Transaction routing does not have several alternatives like function shipping has.
So the case for using this method is more straightforward. If you need access to
a remote transaction, use transaction routing. With this facility, you do not have
to implement the application and data in two places or access two systems.
3.4.7.3 Asynchronous Processing
With asynchronous processing the remotely started transaction does not affect
the application that started it. This facility is useful when it is necessary to start
a transaction without delaying the local transaction at all.
3.4.7.4 DPL
DPL is best used where there is a large amount of data to be manipulated on a
remote system. The DPL program has local access to the data, performs the
necessary manipulation, and returns the result. This process can be
considerably more efficient than having to function ship each item of data.
3.4.7.5 DTP
DTP is the most flexible intercommuncation facility. The programs can send and
receive as much data to each other as required. It is the most complex to set
up, however, as the originating program is responsible for setting up the
communications with the remote system, sending and receiving the data, and
closing the communications down when it is finished.
As a general rule, no matter where the data is located for an application, it is
wise to keep the number of recoverable resources to a minimum. This reduces
the amount of logging that has to be done to protect the updates to the
recoverable resources. Reducing the number of recoverable resources may also
reduce the number of participants involved in any syncpoint processing, thereby
improving performance.
Application data can be held in Encina SFS, in an RDBMS, in CICS queues, or in
a remote system. There are significant performance considerations for each of
these methods. The choice is not always a free one and may to a large extent
depend on where data is currently held. If is not feasible to move data from one
platform to another, the data has to be accessed remotely.
Encina SFS: Data held within an Encina SFS has often been migrated from an
IBM mainframe environment where the data was held in VSAM. The Encina SFS
can be located on the same system as that of the CICS for AIX region. The
advantage of doing this is that the fast local transport (FLT) method can be used
between the CICS application server and the Encina SFS. This method provides
a performance improvement over the use of the DCE RPC.
If the Encina SFS and CICS systems are distributed, it may be possible to use
two smaller machines to provide the necessary processing power. As long as
the Encina SFS and the CICS region are within the same DCE cell, there is no
problem in distributing the components.
Note: Distributing the components may impact the performance of accesses to
CICS files or queues held within the Encina SFS.