We are moving off the Mainframe for a couple of our OLTPs to AIX - the backend is still on DB2.
The problem: Our EDW loads extracted only changed data through IBM's Log Analyzer tool on the Mainframe. Now that this is going to AIX, we will need a CDC mechanism of some kind in the distributed world -
Options I am aware of are -
1. SQL Rep (Free with Db2 LUW, right?) - not very fast? and Only DB2 replication possible
2. Qrep - Licensing purchase - fast and DB2 and Oracle replication
All this is good, however, the OLTP stakeholders are pushing back saying they have a performance concern around the CDC reading the transaction log. I am not given numbers to substantiate this. My understanding is that CDC is an industry best-practice and there would have to be a strong argument against not performing CDC - performance is a genuine concern for OLTPs but would need to established.
In you guys' experience, have you ever seen significant performance problems from conventional CDC ? If so, what was done to remediate?
There is a separate product - IBM InfoSphere Change Data Capture, formerly known as DataMirror, - so don't confuse the three.
It's not clear from your description whether your OLTP systems are the source or the target of replication; I'm assuming the former.
Since SQL replication Capture reads transaction data from the logs that have already been written, I don't see how that can affect OLTP workload (unless, of course, your system is running at close to 100% of CPU and/or I/O capacity, in which case you have bigger problems to solve). You can schedule Capture so as to minimize interference with other workloads.