A question that has come up a few times recently is why does the date modified timestamp on my Exchange databases not change (even though the database is mounted and functioning). Specifically some administrators have been looking at this as an indicator of health on a passive database copy – which it is not.
The date modified timestamp will generally get updated on an Exchange database when one of two things happen:
1) The EDB file size is extended in order to accommodate data that does not fit into whitespace that currently exists in the database.
2) The database is dismounted and all open handles to the file are released.
Note that the modified time is not subject to change if the contents of the file are changed – for example if whitespace is utilized within the database for the storage of new messages etc the date modified will not change.
To show this I used my lab to generate some examples. Here is a screen shot of a database that was mounted last on 8/3/2010. The database screen shot was taken 8/8/2010 before 8:29 am edt.
Using the Exchange Management Console, I dismounted the database at 8:29 am edt on 8/8/2010.
You will note that the date modified changed to the time and date the dismount occurred. I then used the Exchange Management Console to re-mount the database.
After remounting the database I noted that the time remained the same as in the previous screen shot. I then took some test mailboxes with content, and moved them into the mailbox store. You will note in this screen shot that both the size and date modified changed – in this case the database file was extended on the partition so the change was expected.
It is normal for an Exchange database to not show an updated date modified and this field should be used to judge the health or utilization of an Exchange database.