Friday, August 22, 2008
DB2 Stored Procedure Maintenance
If you ever thought that you can just create a bunch of DB2 store procedures and left it in the server until it being replaced by newer version without having to spend some efforts to maintain it, you're wrong, dude/dudette.
Dynamic SQL statement is as it's name implied: Dynamic. Dynamic in the sense that the SQL Compiler process the statement when someone execute it and optimize it using the current statistics.
What about Static SQL statement? Haha, does this start to make any sense?
If it haven't ring any bells in your mind, faster go and grab a copy of DB2 book and start your revision.
Static SQL statement's access plan is generated and stored in the database at the moment that you perform the binding, i.e. compile the statement. This means that the access plan is based on the statistics at that moment.
In a large organization with few ten to hundreds line of business servers, usually the DBA don't really bother (or they can't really know) whether they must perform the maintenance on the application database objects.
Remember the DB2 Automated Maintenance Tool in DB2 Control Center? They only help you to backup, reorg and runstats your databases. Frankly speaking, there are more maintenance needs than you possibly can imagine.
Just like human body which you gotta do exercises, body building and drink super boosted tonic to maintain that drop dead gorgeous figure to attract the opposite sex, any enterprise databases desire the same treatments.
I'm going too far, but you get the idea, :p
So, the meat for today's lesson is: YOU HAVE TO REBIND YOUR STORED PROCEDURE, especially those lengthly multipages SQL codes and which involves plenty of data manipulations. One good example is a taxing month-end report generation SP.
To do this, you must either recreate the stored procedure which is I think a stupid way to perform in the long run, or you can use the System Procedure: SYSPROC.REBIND_ROUTINE_PACKAGE like the example below:
Of course, there are few calling variants by passing in different set of parameters, but the whole point is you need to rebind the SP.
And..... very important, in case you are new in this field. Make sure you reorganize your tables (i.e. REORG command) and collect the latest statistics (i.e. RUNSTATS command) before you do the rebind, else it won't help much.
DB2, Simple right?