In a world where everything
has become real-time, mainframe is fast catching up to the term near real-time.
It was not long ago, that customers were asking for real-time information. This
did have an impact on mainframe community too, Db2 or Adabas, the word was out
to see if a replication mechanism can be developed and if such a replication is
a viable option. Software AG (developers of xml & Adabas/natural) was able
to size up the opportunity quickly by creating the new tool called Adabas
replicator driven on PLOG. Db2 wasn’t far behind either.
The only cliché was that
Adabas Replicator was yet another tool (well let us say you have to get a licensing
cost to it) to be marketed by the software giant, while db2 provided a solution
called event publishing for converting committed source changes into messages
in an XML format and publishing those messages to applications such as message
brokers by leveraging the system files within db2. Before I proceed further, I just
want to pause and say this – in both the instances the replication is only near
real-time and it really depends on the target systems, on how fast they can
process the messages from the queue.
A simple configuration of
event publishing looks like this:
DB2 MQ setup table : SYSIBM.MQSERVICE_TABLE
DB2 ID used by db2 to access
MQ = DB2MSTR
Sample DDL Set up as follows:
CREATE TRIGGER “REF_DATA_TRIGGER”
AFTER INSERT ON “REF_DATA”
REFERENCING NEW AS REF_NEW
FOR EACH ROW MODE DB2SQL
BEGIN ATOMIC
SELECT DB2MQ.MQSEND
(
'MYSERVICE',
CAST(‘<REFDATA>’||XML2CLOB(
XMLCONCAT(
XMLELEMENT(NAME “FIELD1”,REF_NEW.FIELD_1),
XMLELEMENT(NAME “FIELD2”, REF_NEW.FIELD_2),
XMLELEMENT(NAME “FIELD3”, REF_NEW.FIELD_3),
XMLELEMENT(NAME “FIELD4”, REF_NEW.FIELD_4),
XMLELEMENT(NAME “FIELD5”, REF_NEW.FIELD_5),
XMLELEMENT(NAME “FIELD6”, REF_NEW.FIELD_6)
))||’<REFDATA>’ AS
VARCHAR(2000)))
)
FROM
SYSIBM.SYSDUMMY1
Special thanks to my colleague
Jeegar Doshi who helped me compile
the information on DB2 replication.
