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

Table 5. XA-enabled and Non-XA-Enabled Relational Databases
XA-Enabled
Relational Database
Transactional information exchange between
CICS for AIX and DB2 for AIX takes place.
Coordinated commitment or rollback of both
CICS resources and RDBMS table changes
occurs through the EXEC CICS SYNCPOINT call.
An XAD entry (Product Definition) is required
for each database. CICS for AIX has to be cold
started after any changes to the XAD stanza file
or the addition of new XAD stanza file entries.
Provides better performance because CICS
transactions can reuse an XA-managed
database connection while the application
server (cicsas) is running, without having to call
EXEC SQL CONNECT repeatedly.
CICS immediately abends the region if it cannot
open a connection to the database.
CICS facilities for transactional control must be
used. These are the EXEC CICS SYNCPOINT
and EXEC CICS SYNCPOINT ROLLBACK
commands.
CICS SYNCPOINT processing takes longer than
an SQL COMMIT call because it includes
coordination of syncpoint among all resources
managers involved.
CICS application programs must be compiled
with the NOSQLINIT option.
Database connection stays with the application
server (cicsas). Hence it is conveyed across an
EXEC CICS LINK or EXEC CICS XCTL call.
Database connection is established according
to the XAD definitions at CICS startup time.
There is no need for the CICS transaction to
make the database connection.
Non-XA-Enabled
Relational Database
Transactional information exchange between
CICS for AIX and DB2 for AIX does not take
place.
CICS application has to issue EXEC SQL
COMMIT call or EXEC SQL ROLLBACK call
explicitly for the changes of RDBMS tables.
Only the CICS resource changes are affected
by the EXEC CICS SYNCPOINT call.
An XAD entry is not required. A CICS
application that wants to connect to a particular
database has to issue an EXEC SQL CONNECT
call.
CICS applications have to issue the EXEC SQL
CONNECT call to start the database connection
for each transaction. Hence there is a greater
overhead.
CICS region keeps running when the EXEC SQL
CONNECT call issued by a CICS application
fails.
RDBMS facilities must be used. They are the
EXEC SQL COMMIT, EXEC SQL ROLLBACK,
and EXEC SQL SYNCPOINT commands.
SQL COMMIT processing is faster, but it only
works if no other resource managers are
involved in the transaction. Furthermore, using
SQL COMMIT in a transaction prevents you
from issuing an EXEC CICS SYNCPOINT call in
the same transaction.
Special compile options are not required.
Database connection cannot be conveyed
across the EXEC CICS LINK or EXEC CICS XCTL
call. You must disconnect from the database
before these calls and reconnect in the called
program.
CICS transaction has to connect to the
database through an EXEC SQL CONNECT call
before making any SQL access calls.
Chapter 7. Interactions with the DB2 Family of Products 93