Before Image & After Image files

TomBascom

Curmudgeon
Undo log and redo log.

There is an "old wives tale" that truncating the bi file nightly is good or even necessary. This is false. It is actually sort of harmful to performance since the first users of the database will have to wait while the IO to expand and format the necessary disk space occurs.

A bi file has a "natural" size for your workload. It varies depending on many factors so there is no simple rule of thumb for predicting it but if the bi file is less than 1GB don't worry about it.

In normal operation you should never truncate the bi file unless:

1) An unusual circumstance occurs which grows it far beyond its "natural" size
2) Some maintenance operation requires you to

If you do decide to truncate the bi file for some reason use the bigrow option afterwards to regrow the clusters so that users won't have to wait.
 
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