Error ID 9646

Article
2017-08-29

Question

_{Tuesday, August 29, 2017 10:19 AM}

Hi,

We have Exchnage 2016 Version 15.1 ‎(Build 225.42)‎.

We have Error ID 9646:

Mapi session /o=DotinEX/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=XXXXXX with client type OWA exceeded the maximum of 16 objects of type Session.

I add this key and DWords in registery Exchange server :

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystemkey=MaxObjsPerMapiSession , Dwords :objtFolder,objtFolderView Dwords :MaximumAllowedSessionsPerUser

and Restart Microsoft Information store and restart Exchange server, but It is not resolve.

How can Resolve It?

Thanks.

All replies (6)

_{Tuesday, August 29, 2017 12:30 PM}

To revert to the default configuration

Open a registry editor, such as Regedit.exe or Regedt32.exe.
Navigate to:

HKLM\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\MaxObjsPerMapiSession.
Delete the objtFolder registry value.
Close the registry editor and restart the Microsoft Exchange Information Store service for the change to take effect.
Alternatively, if you wish to make use of the objtFolder registry value, instead of deleting it, keep it set to its existing value or adjust it as needed.

https://technet.microsoft.com/en-us/library/aa996193(EXCHG.80).aspx

Next method:

Details: MAPI session "Mapi session /o=DotinEX/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=XXXXXX with client type OWA exceeded the maximum of 16 objects of type Session. ". If you notice, the objects of type is session. Would this fix apply to this also?"

1. Click Start, click run, type regedit, and then click OK.

2. Expand the following registry subkey:

HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

3. Right-click ParametersSystem, point to New, and then click Key.

4. Type MaxObjsPerMapiSession, and then press ENTER to name the new subkey.

5. Right-click MaxObjsPerMapiSession, click New, and then click DWORD Value.

6. Type Object_type, and then press ENTER to name the object.

Note:

Object_type is the name of the object type in the error message that is mentioned in the "Symptoms" section.

_{Tuesday, August 29, 2017 12:34 PM}

This issue occurs because the default maximum number of connections that an account can open was exceeded.

An account can open a maximum of 32 connections to the Exchange Information Store.

Use the Maximum Allowed Sessions Per User registry key.

STOP: Incorrectly editing the registry can cause serious problems and may not be able to be resolved so BEFORE editing the registry, back up any valuable data and the Registry so that you can roll back if needed.

1. On each Exchange mailbox server, create the registry DWORD value called Maximum Allowed Sessions Per User under the following registry key: \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

2. Set Maximum Allowed Sessions Per User to 0x00001388 to allow up to 5,000 sessions per user and of course you should probably use a lower # once you confirm this is working and here is an article from our site as well https://www.lucid8.com/documentation/DSWebHelp/SETUP/Maximum_Allowed_Sessions_Per_User.htm

Lastly you may also need to consider making a throttling policy for the user(s) involved and to that end check out this link we give to our customers for making a custom throttling policy for a special user we call DSAdmin but really it can be anything http://www.lucid8.com/documentation/DSWebHelp/TRO/Exchange_Client_Throttling_Settings.htm

Search, Recover, Export Mailboxes, Folders, Email, Contacts, Calendars, Tasks, etc. from Offline Exchange Databases (EDBs), On-Premise Exchange Servers and Office 365. Migrate/Recover direct from any offline EDB into any On-Premises Exchange Server, even cross version i.e. 2003 → 2007 → 2010 →2013 → 2016 → Office 365 with Lucid8's DigiScope

_{Wednesday, August 30, 2017 5:09 AM}

Hello,

Is it Correct ? and the value for Object_type=1000 is OK?

_{Wednesday, August 30, 2017 8:48 AM}

Hi,

You almost there. Add a DWORD entry named Maximum Allowed Concurrent Exchange Sessions Per Service with a decimal value higher than 16.

Please refer to:

Hope it helps.

Regards,

Jason Chao

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_{Thursday, September 7, 2017 5:13 AM}

Hello.

I create it, and restart server but the problem is not resolved.

_{Friday, September 8, 2017 2:10 AM}

Thanks for your reply.

It's recommended to restart the server in down time and check the results.