So you have a 300 SQL statement script that runs fast on SQL Server, but the same SQL script is slow on DB2 when you run it? Be careful what you say on these forums you'll get boycotted for such blasphemy by the "IBM i is best server on planet folks".
Joking aside, here is a few things I can think of:
1. Are you running the SQL statements against DDS described files in DB2? If so, this might be a performance problem as there are likely no SQL indexes on those files, and DDL described files can use much larger page sizes (64KB if I recall), so your problem might be there.
2. Are the SQL statements really the same? It seems to me you might be comparing SQL statement execution to that of an RPGLE program execution doing the old CHAIN's, SETLL, etc type of logic which is nearly always going to be slower than doing it via SQL statements.
3. Why are you making a work file? Is the SQL Server equivalent creating work files as well? Because if you have to delete/create these perhaps that's where the extra time is being consumed?
Matt
-----Original Message-----
From: Peter Connell [mailto:Peter.Connell@xxxxxxxxxx]
Sent: Wednesday, May 29, 2013 2:48 PM
To: Midrange Systems Technical Discussion
Subject: RE: Performance question and SQL SERVER
I've have an SQL script that runs considerably faster on SQL Server that than on system i.
I have 300 SQL statements which must be run each time a transaction is requested by the client and the response is slow. It is problematic to convert these 300 to native RPGLE which I know would perform well.
The client makes a usual inquiry against a consumer database and a report is generated from matching detail entries on several database files. The report was developed long ago with RPGLE.
But now the RPGLE creates a work file of a few hundred values deemed as significant which are derived from the same data source. The work file is repopulated for each client transaction and its content depends on each new client request, so it differs each time.
Each of the 300 SQL statements (which in fact are supplied by a 3rd party) defines a separate business characteristic that uses SQL to join the work file entries to a predefined table of attributes and return a summary result value.
The net result is that, in addition to the report, a further 300 characteristic values can be returned that relate to specific client request.
Unfortunately, all 300 statements can take about a minute to complete which is too slow. However, if the same transaction is repeated then the same result can be returned in about 5 seconds.
Diagnostics from running in debug mode show that a repeated request reuses ODPs. Unfortunately, when a new work file is created for the next client transaction, these ODPs get deleted and the transaction is slow again.
I've tried playing around with activation groups , shared opens via OVRDBF and using an running a pre-requisite OPNDBF but had no success in reducing the transaction time.
I am perplexed by the fact that we have a developer familiar with SQL server who has demonstrated that he can easily create a script that runs all 300 statements on SQL server in just a few second with no performance problems. Why is that?
Peter
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Hoteltravelfundotcom
Sent: Thursday, 30 May 2013 12:38 a.m.
To: Midrange Systems Technical Discussion
Subject: Performance question and SQL SERVER
Has anyone ever ported AS400 data to a SQL Server? Why would you do that, because of the company having some extra servers that can be used as either Replication, or to use for reporting tools based in Windows.
If so, are there tools or products for this or something one can do on their own.
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