What do the Database Engine Advanced options do?

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What do the Database Engine Advanced options do?

Postby Pete Tabord » Thu Sep 13, 2007 9:46 am

These are mostly settings you should never need to set! Even the ones that do make a noticeable difference are only likely to be of use in large applications. By large we mean with loads (>100,000 at least) of records, not necessarily lots of documents.

This is what they do.

Statistics:Running Total:

off: Statistics are calculated only when asked for
on: Statistics are calculated as running totals.
Subtle difference - no noticeable effect in most cases.

Statistics:Keep Last Record

If its 'on' it keeps the last record in a group or Subform in memory so that you can put its values on trailers etc. Applies to procedures only. Much better to use summary variables or LOV's in practice.

Sorting: Buffers

This one is more significant - basically, the more you have the faster you go, but the more memory you use. If your application has lots of records and frequently uses in order or in reverse then increasing this value can noticeably improve performance

Procedures:Free Subform Records.

If its 'on' then the rows in subforms are refreshed after each processing pass if it's off they are cached. This in effect controls how 'up to date' information is when processed by a Procedure - off is faster but the data might be slightly old.

Procedures:ScanQuitRatio

Another significant one. This controls the use of indices - for example, the default is 25% . This means that when the amount of records selected by a given Procedure exceeds 25% of total number of records in the Form, the indices will not be used (because typically it would then be faster to do a flat scan of the records). Performance can be improved (or harmed) by varying this ratio - it may be worth adjusting if you have many reports that select a lot of records.

Remember indices don't speed things up much anyway unless you have at least a few hundred records. The extra overhead of opening and so on counteracts the speed gain of going straight to the record.

MultiView Buffering Options

Currently not useful because they are all maxed out - they will be of more interest later.

Regards
Peter J. Tabord
Head of Development
Database Software Ltd.
ptabord@ffenics.com
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