Outlook recurring appointment problems

Rafal_Mitura used Ask the Experts™
when clicking on a recurring entry on a public folder calendar the following message pops up
"Cannot read one instance of this recurring appointment. Close any open appointments and try again, or recreate the appointment."
this has been a problem since our exchange domain migration and seems difficult to fix... any ideas would be good!
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Are there a large number of instances of the recurring appointment that have been modified from the original recurrence schedule?  If so, you could be running into an interesting limit problem.

Basically, with a recurring appointment each occurrence that has been modified is treated as an "open message".  Exchange has a maximum value set for simultaneous open messages (250 by default) which can be modified in the registry.

It's fairly easy to fix this and test it to see if this is you problem.  On the Exchange server, perform the following steps:

  1. Open regedit
  2. Locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
  3. On the Edit menu, point to New, and then click Key.
  4. Type MaxObjsPerMapiSession, and then press ENTER.
  5. On the Edit menu, point to New, and then click DWORD Value.  Name the new value "objMessage" and set it's value to something higher than 250 (this limit shouldn't impact performance unless you have a script of some type that retrieves large numbers of messages at once; I'd probably set it to 500 or 1000 for now).  Make sure you are setting the value in decimal.
  6. Close Registry Editor.
Try your recurring appointment again.  If this fixes the problem, you may also want to look into Auto-Archiving old appointments, to avoid hitting the new limit again.


P.S. I ran into this problem myself a few weeks ago on one of our clients' Exchange server.  Here are the reference articles I found that led me to try this fix:





Thanks very much for your help, the user was happy to edit it using Web outlook.. fair enough! and i have edited the limit to a higher number for future reference.
Thanks Muchly
I know I pulled some hair out when I first butted heads with this issue, so I'm glad I could help save someone else some of the same trouble.


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