Data is not migrated to Exchange Server 2010 and "WARNING: [4965-24-60-80040111] Unable to ope (4235243)

Notes Migrator for Exchange might not migrate some mailboxes to Exchange Server 2010 and the following warning message might be displayed in the migration logfile:

14:20:36 WARNING: [4965-24-60-80040111] Unable to open target mail store
14:20:36 OpenEntry(Inbox):
14:20:36 MAPI error 80040111
14:20:36 Error: Microsoft Exchange is currently busy. If this message is still displayed in 30 minutes, contact your Exchange administrator.
14:20:36 Component: Microsoft Exchange Information Store
14:20:36 Low level error: 80040111
14:20:36 Context: 00000520

Subsequent migrations of the same mailbox might just work fine.

Microsoft Exchange Server 2010 has connection limits set in the registry which stop Notes Migrator for Exchange from connecting to mailboxes once the limit is reached.

The registry key in question is szMaxAllowedSessionsPerUser which default value is set to 32. So, if there are for example, 5 migration consoles with Notes Migrator for Exchange running, and each console is configured to use 8 threads (8x5=40), this would already exceed the limit and lead to the MAPI error above.

This value can vary up to 65k and can be increased.

More information can be found here: http://technet.microsoft.com/en-us/library/ff477612.aspx#SL
 

RESOLUTION

Increase the value for szMaxAllowedSessionsPerUser so that it matches the migration scope.

Please note that this limit does not affect users included into the Exchange Enterprise Admin group, as the storage admin for mailbox role is not affected.