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Robert Reisig

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Outlook 2007 - large OSTs, sync problems

In our environment we have a client who manages multiple calendars, that is, she is a delegate for 9 different execs and manages 9 calendars in Outlook.  Exchange server is v2010, Outlook is 2007 SP2 on all workstations.

We are finding that the user has periodic problems with sync of changes she makes to the execs calendars; from time to time she will schedule a meeting or change a meeting on one of their calendars and while the invites and updates go out to the attendees, and the copy of the exec's calendar in her local OST folders is updated, the meeting is not synced to the exec's Calendar folder on the server.

I noticed that the user's OST is larger than 5GB, which I found unusual, I rarely see OSTs in that range.  I also noticed that in the user's Windows Event Log, there are multiple instances of an event that says that the OST is being reconciled with the indexer because the store was last opened on a different machine - an impossibility, since the OST is on a local hard disk and not shared with any other computer.

Looking for suggestions on resolving this - my theory is that the OST is so large that Outlook can't effectively and efficiently sync it against the Exchange servers, or possibly that the OST is corrupt.
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Have you disabled cache mode and tested?
If that runs well, then it is most likely the OST is corrupted. Trash it and create a new one from scratch.
OST files (like PSTs) are prone to corruption.
A the start of a day (or start or lunch break), close Outlook for that user and locate and rename her OST file.
Start Outlook up and allow it to rebuild a new OST.

Ensure that the OST file is not scanned by Anti-Virus on her PC.
Ensure that she is not indexing her mail from a desktop search engine.
Personally, for a Workstation, I dont like to use CEM, because of the common corruption that they are prone to.
And sure she has never logged on to another workstation before, and used Outlook?
As explained by "diverseit",  Just disable cached mode and test, if it is OK then definitely there is some problem with OST file. You just have to delete(backup here is recommended) the ost file and enable cached mode and when you reconnect with the Server, Outlook itself creates a new OST file that contains all your mailbox data. But the data you have in the non-synchronized ost file will be lost.

To get back that data you need a OST file converter utility, Although as per my knowledge there is no such free utility. You must have to approach third party organizations for that. One such tool is there for evaluation and to convert ost to pst file.
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Robert Reisig


Thanks for the quick responses, folks! Some responses -

Diverseit - we did try with cache mode off and while the user's access to those delegated calendars is working consistently performance becomes intolerably slow. In our environment, we are required to use offline mode - believe you me I'd rather not, but we have no choice in this matter.

Postmaster - Agreed and I often have observed same. Now, on your indexing comment - WIndows Desktop search is in fact indexing that super huge OST; now, I want to turn it off but I have been told if yo do not use Windows Desktop Search Outlook 2007 and 2010 do not properly return search results when you use the quick search or advanced find tools; do you know otherwise or have other information on this? I experienced this a bit myself; if I turn WDS off, I find searches for things that are right before you in the inbox return 'not found' results.

Johnb6767 - confirmed; she never uses any other computer, it was easy to confirm and determine this. Also, I can't imagine how that other computer would get configured to use an OST on another computer's C: drive; my desktop support team doesn't even seem to know how to do that.

Jennylembert - As noted above and agreed on all points. I this case I had to use scanost and fix it, as there was data to be recovered and synced to the user's execs who have delegated calendars to her.

To summarize on this point, since I think this brings it to a point - we have actually done what Jenny suggests several times over a year for this user, delete OST and start again and inevitably the problem returns. We have also upgraded her twice over the year to brand new computers with clean, corporate approved and tested images and the problem always returns. I'm wondering now if there is an undocumented limit or issue with large OST size, or if there is a known issue with managing 9 calendars - I've never seen another assistant manage so many on one computer in one Outlook config, and these calendars are unbelievably complicated and full of content.
There is a limit on each directory size. No directory should be over 5.000 items.

I would also setup archiving on her account to reduce the size.
OST & PST get corrupted, especially on large files.
How did you setup the max file sizes for OST/PST? Take a look at these articles to shed more light on OST sizes.
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This is just what I was looking for, good data and complete info on large OSTs. As noted this one is the winner when it comes to size, I never work with any over the 2GB range; also, for what it's worth and as noted we have to use cache mode - we tried running this user without it last year and performace is intolerable when she's switching between the * 9 calendars * she manages (again, largest # I've ever delt with in any environment).

Thanks for the points! Glad I could help.
"Also, I can't imagine how that other computer would get configured to use an OST on another computer's C: drive"

If CEM is enabled, the OST file gets created on it's own.....

Glad you got the answer.....