Hi, Can anyone tell me about the msExchESEParamMaxSessions limit on Exchange 2010? I've seen this message a few time in the Event Log, and I can't find anything recent about it on the internet, only information pertaining to versions up to Exchange 2003. Kind Regards, Nick Douma

When you do you see the event log messages? During backups or AV scans? Can you post the exact event?

The exact event is: No database session was available to satisfy a request on the mailbox database 'Mailbox Database 1'. The number of sessions configured via the Active Directory attribute msExchESEParamMaxSessions on the database may be set too low for the level of activity on this database. This is during normal operation, and usually a minute after this message we receive a Error 1100 while attempting to compute free space for database "Mailbox Database 1". Database path: 'I:\mailbox database 1\'. After which we experience a loss of service for all boxes on that Mailbox Database, and have to move it to another server and back to fix it.

Having worked with this error myself, I recommend not trying to change the limit, but instead look at what might be causing the issue. For us, it was too many mailboxes (number, not size) on a logical disk. The disk couldn't handle the IO. Splitting the number of user into two databases instead of one resolved that issue for us. Also, you might want to take another look at the amount of RAM in the MB server hosting that database. Make sure it meets the requirements for DB Cache for the number of mailboxes its hosting.

Agree with ty72182 Do not play around with Adsiedit.msc and yes if you have too many mailboxes in one Database, split them into different mailbox database. PLEASE Post the entire Event IDGulab | MCTS-MCITP Messaging: 2010 | MCTS-MCITP Messaging: 2007 | MCC 2011 | Skype: Gulab.Mallah | Blog: www.ExchangeRanger.blogspot.com

The entire events are: 20110526093655.000000 Category=6 CategoryString=General ComputerName=mbx1 EventCode=1164 EventIdentifier=-1073347444 EventType=1 Logfile=Application RecordNumber=817720 SourceName=MSExchangeIS Mailbox Store TimeGenerated=20110526073655.000000-000 TimeWritten=20110526073655.000000-000 Type=Error User=NULL wmi_type=WinEventLog:Application Message=No database session was available to satisfy a request on the mailbox database 'Mailbox Database 1'. The number of sessions configured via the Active Directory attribute msExchESEParamMaxSessions on the database may be set too low for the level of activity on this database. The current value for this parameter is 449. 20110526093716.000000 Category=15 CategoryString=Background Cleanup ComputerName=mbx1 EventCode=10017 EventIdentifier=-1072748767 EventType=1 Logfile=Application RecordNumber=817723 SourceName=MSExchangeIS Mailbox Store TimeGenerated=20110526073716.000000-000 TimeWritten=20110526073716.000000-000 Type=Error User=NULL wmi_type=WinEventLog:Application Message=Error 1100 while attempting to compute free space for database "Mailbox Database 1". Database path: 'I:\mailbox database 1\'. The server specs are in line with Microsoft recommendations, and our cache hit ratio is 99.99% most of the time.

http://www.microsoft.com/technet/support/ee/transform.aspx?ProdName=Exchange&ProdVer=8.0&EvtID=1165&EvtSrc=MSExchangeIS&LCID=1033 In our case we could never get the calculations to match the errors in the event log. Once again, rather than changing values from defaults, we split up the load. We had BES, ActiveSync, and Unity all to consider in our calcuations, not to mention online v. cached outlook users etc...

Hows the issue now? Gulab | MCTS-MCITP Messaging: 2010 | MCTS-MCITP Messaging: 2007 | MCC 2011 | Skype: Gulab.Mallah | Blog: www.ExchangeRanger.blogspot.com

Hi Cyso, Any updates? If you installed some 3rd party softwares on the Exchange server, please stop them first to check whether the event will be gone. About the event 1164, you can also try to increase the value. Please see: http://www.microsoft.com/technet/support/ee/transform.aspx?ProdName=Exchange&ProdVer=8.0&EvtID=1164&EvtSrc=MSExchangeIS Please also run the Exbpa in the Toolbox to do a Health check. Frank Wang TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

We have no 3rd party software that we can disable on the servers. We're currently in the process of creating a new database on a new server, and moving our top users to that database. So far, it seems that this is indeed decreasing the load on our other two databases. We'll see how that goes, particularly on a day where there is more activity than today. I've also ran the Exbpa, and fixed the missing homeMDB issue for the new database. Apart from that, there are no issues.