Working with a client recently, we came across some unusual behavior with one mail file. The user reported that his database had gotten to be 64GB and he wasn't sure how.  Looking at the database properties, it did show up as 64GB, but there were only around 10K documents and the percent used in the database was around 3%.  Something wasn't quite right.

Running a compact -c managed to get the database back down to around 2 GB, but over a few days, the database grew again to where it was 7 GB with no document growth as the user was archiving documents as well.  I created a new replica of the database and monitored the size for a few days and it remained steady, nothing like the original.  Looking at the database properties on the original database, I found that the Advanced Database property to "Optimize Document Table Map" was checked for some reason. This isn't the normal setting for a mail file, and apparently there's a reason for it.



While this setting is supposed to improve performance of databases, in this case it didn't. This may be due in part to the use of views that are Form specific can cause too many documents to be eligible for inclusion in a view - I'm not a developer so I can't be definitive about it.  

To fix this issue, a compact -f was executed to disable the setting and correct the database size. After that was done, the database has seen "normal" growth since.

So the lesson here is - just because you read that something is good for you, doesn't always make it so.