Event ID - 8213

Event Id8213
SourceEXCDO
DescriptionCalendaring agent failed to update the free/busy cache during an appointment save or delete operation.
Event Information"According to Microsoft:
CAUSE 1:

This issue can occur if the MSExchangeFBPublish key or its subkeys are missing from the Microsoft Windows registry:
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeFBPublish
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeFBPublish\Parameters
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeFBPublish\Parameters\server_name
The missing value is:
Name: SystemAttendantDN
Type: REG_SZ
Data: /O=Organization/OU=Administrative Group/cn=Configuration/cn=Servers/cn=server_name/cn=Microsoft System Attendant
RESOLUTION :
To resolve this issue, restore the correct registry settings on the computer that is running Exchange 2000 Server. To do so, you need to edit the registry.
Warning :Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To restore the correct registry settings:
1. On the computer that is running Exchange 2000 Server, start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
3. Right-click Services, point to New, and then click Key.
4. Name the key MSExchangeFBPublish.
5. Click the MSExchangeFBPublish key, right-click the MSExchangeFBPublish key, point to New, and then click Key.
6. Name the key Parameters.
7. Click the Parameters key, right-click the Parameters key, point to New, and then click Key.
8. Name the key your_server_name, where your_server_name is the name of the Exchange 2000 server.
9. Select the your_server_name key, right-click the your_server_name key, point to New, and then click String Value. Add the following string value:
Name:
Reference Links"You receive an ""unable to perform the operation"" error message when you save Calendar items in Exchange 2000 and Exchange 2003

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