The information store dismounts and starts referencing "version store" errors similar to the following event:
Event ID 623
Information Store (2356) The version store for instance 0 ("ca192ae5-ad76-478e-8530-0b1756e7d28d") has reached its maximum size of 85Mb. It is likely that a long-running transaction is preventing cleanup of the version store and causing it to build up in size. Updates will be rejected until the long-running transaction has been completely committed or rolled back.
Possible long-running transaction:
SessionId: 0x111006E0
Session-context: 0x00000000
Session-context ThreadId: 0x00000B64
The Application log may also contain a series of MSexchangeIS events (#1022) and MSexchangeSA events (#9175).