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Message Posted: Mon, 24 Oct 2005 @ 18:08:37 GMT


     
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Subj:   Re: SQL Assistant interferes with other apps
 
From:   Dempsey, Mike

We first noticed this 'slow down' effect on anything that was done in the DOS command window last week. (We had not noticed a delay in 'File' operations ... but that would make sense since these are also command operations.)

I ran tests on different versions of SQL Assistant and founds that the slowdown started in version 7.0.

After comparing the code between the different versions it appears that it is (somehow) caused by the fact that 7.0 passes Unicode strings to the (Microsoft) ODBC Driver Manager, whereas 6.2 passed ASCII strings. Everything else - including the fact that I give up control of the CPU for 50ms within each loop to check whether the query has completed - is identical.

The app itself is compiled using the exact same version of the compiler, so the difference is apparently 'outside' the application. I would have expected it to be slightly more efficient, if anything, since the strings within the app always were in unicode - so we no longer have the unicode to ASCII conversion to perform. (This was performed automatically by the Visual Basic runtime.)

The ODBC driver manager will now use different logic - but I know nothing about its internals. (That would be a Microsoft question) I dont see why it should cause a slowdown of any other app though.

I also ruled out a problem with the ODBC driver itself. I used the latest driver with SQLA 6.2 and there was no problem. I also used the 3.3 (ASCII) driver with SQLA 7.0 and the problem occurs.

The only common element appears to be the Microsoft ODBC Driver Manager.

I am currently experimenting to see if changing the loop delay time helps at all... but as you noted - SQLA is not consuming much CPU at all, so I doubt this will help.

(The 'odd' behaviour of the scroll bar while another query is running would be caused by the 50ms delay. The appearance of characters typeed into the Query window would also be expected to be a little slow for the same reason... I just cant explain how it can effect the command shell.)


Mike Dempsey
Teradata Client Tools



     
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