RECOVER QMGR(TUNE READAHEAD ON)
IBM Data Replication Answers
A new WebSphere MQ enhancement may give Q Replication a significant throughput boost in those situations where you have either (1) workload spikes that increase replication latency or (2) changed data that has built up in queues because of the temporary unavailability of a target database. The new feature is tailored for the sequential access of messages and causes MQ to read messages into the MQ buffer before the messages are needed. This method lets both the Q Apply program and MQ channel agents pull messages from memory instead of disk.
Why is this possible? When the number of messages overruns the buffer pool allocation for the queue, messages are spilled to disk and must then be retrieved from disk when needed. With the read-ahead enhancement, messages can be in memory. In addition to greatly improving throughput in these situations, the enhancement lowers overall replication latency. This new MQ feature also benefits performance at the source transmission queue.
In our test, we achieved the 55 percent increase in rows per second processed by Q Apply on a DB2 for z/OS Version 9 non-data sharing system with Q Replication Version 10.1 and WebSphere MQ Version 7. The average message size for the test was 50K. We have observed significantly higher improvements in replication throughput with smaller messages, for example 10K. Your throughput numbers could be noticeably different from these because replication performance can be heavily influenced by environment, row lengths, replication configuration, and more.
For more information, see the text for APAR PM63802.
The buffer pool read ahead enhancement is available starting with WebSphere MQ V7 APAR PM63802. You can enable the function by issuing the following MQSC command:
You can add the read ahead function to both the source and target queue managers for optimal performance. No changes are required to your Q Replication environment to take advantage of this feature.
DavidT 120000JC6D Tags:  oracle data_replication mq infosphere_warehouse db2 datastage q_replication event_publishing 1 Comment 4,866 Visits
This post is not about whether you need some kind of event publishing* function for DB2. It's about whether you already have the function found in InfoSphere Data Event Publisher and just don't know it.
InfoSphere Data Event Publisher is built from IBM's Q Replication technology. More specifically, it provides a subset of the function found in the Q Capture program. The question is, if event publishing is a subset of Q Capture and I already have Q Replication, do I need to buy Data Event Publisher? The answer is almost always no. Why "almost always"? Q Replication is found in several IBM products and features. For example, no-cost, two-site Q Replication was recently added to certain editions of DB2 and InfoSphere Warehouse. Some of these products have license restrictions on how Q Replication function can be used. I have the products listed here along with the answer about whether you need to buy Data Event Publisher with it:
Wait... what? I can do replication with Q Capture's event publishing? Yes :) but the primary reason you would consider this is when you want to run data through a transformation engine such as InfoSphere DataStage and don't want to run an apply program at the target or stage data in tables or files. The following picture shows an example of what I mean:
* For those of you who aren't sure what data event publishing is, it's function that lets you capture changed data from a database log and publish it to consuming applications. The format of the published data is such that you can determine transaction boundaries, see the SQL operations (insert, update, delete) as well as the order they occurred, and have both before and after values for updates. Depending on the tool you use, data can be published to relational tables, WebSphere MQ, or flat files. The consuming app (or apps) can be one you develop such as for SOA or an off-the-shelf app like InfoSphere DataStage.
This post focuses on publishing to WebSphere MQ queues because that's what's found in InfoSphere Data Event Publisher.
(Oh, I can hear the outcry now... people saying that no one's ever used the term event publishing when the destination is tables or files. Seriously? Those are just staging mechanisms. They don't change the end result. You still get data events published. And those events are still available to consumers. For comparison, see the IOD 2010 presentation about providing changed data to InfoSphere DataStage via tables.)
DavidT 120000JC6D Tags:  licensing q_replication warehouse mq wmq mqseries what_do_i_need infosphere webspheremq db2 1 Comment 4,684 Visits
This post is the answer to one of the FAQs found in
Yes, a limited-use copy of WebSphere MQ comes with all products that license use of Q Replication. "Limited-use" of MQ simply means that you can only use this copy of MQ with Q Replication. However, some products allow a few other things, too. For example, most DB2 LUW and InfoSphere Warehouse editions bundle MQ because DB2 LUW has a several integration points with MQ, not just Q Replication.
Do you have to use the bundled copy of MQ? No. If you already have a fully licensed copy of MQ, Q Replication will work with that. The one thing to remember is that a best practice is to have dedicated queue managers for Q Replication. In other words, create new ones, don't use queue managers that have other work going through them.
For UNIX and Windows, do you have to install the WebSphere MQ server software on the same system as where Q Replication is installed? No. The MQ server software can be installed on a different system and queue managers created there. Q Replication will access those queue mangers through MQ client software installed on the same system as Q Replication. However, for optimal performance, queue managers should be co-located on the same system(s) as Q Replication. For those of you who want an example of what's allowed, here's one :)
For z/OS, are there any special considerations? Yes, but only for how you order the bundled copy that comes with a z/OS product. See the last heading of this post for ordering information.
How do you verify everything I just said about licensing? :) Check the IBM license information documents. They are the official and final word about what you're entitled to. In fact, what they say overrides anything anyone says in a blog :) You can find IBM license information documents on ibm.com by using IBM's search interface:
Simply enter the product name and date, then follow the on-screen instructions. To read the MQ related terms, search for the string 'MQ'. Here are links to two license information documents that tend to be of interest to people:
You may want to use a date range to limit the results returned.
Ordering Considerations for z/OS
If you plan to use the copy of MQ that comes with InfoSphere Replication Server v10 for z/OS, please note that Replication Server is in Shopz's DB2 zone and the bundled WebSphere MQ is in Shopz's MVS zone. For example, Shopz will show something like the following in the DBS DB2 group/zone:
Shopz will show something like the following for MQ in the MVS group/zone: