arcserve-KB : How to resolve exchange mismatch errors in RHA where there is an exchange prefix mismatch

Last Update: 2016-04-25 13:57:29 UTC

Microsoft Exchange assigns prefix numbers to each mailbox store or public folder store.  The first store created on each exchange server would automatically be assigned prefix e00, the next store e01 and so on.  Sometimes a user removes a store that was assigned an earlier prefix and it can make it hard for RHA to fix an exchange prefix mismatch issue in this case.  For instance, a user has 1 mail store and 1 public folder store on the master using prefixes e01 and e02 respectively.  If the replica has no stores yet while you are creating the scenario we will attempt to create the stores on the replica for you so the 2 servers have the same stores setup.  When we try to create the first store on the replica exchange will want to assign it prefix e00, the next prefix would get e01.  When you try to run this scenario you will then get a message that there is an exchange mismatch and this error usually will show you the prefixes for each server so you can see that there is a prefix mismatch.  This article will provide some ways to resolve this type of issue when it occurs.

  1. One way to resolve this type of prefix mismatch where none of the masters stores use prefix e00 is to create a temporary store on the replica so it gets assigned e00.  If you then manually create the other 2 stores on the replica or use RHA's scenario creation wizard (or autoconfig replica option for already created scenarios) you will then be able to assign the proper prefixes to the stores on the replica.  When complete you can simply remove the temporary store you created on the replica and then both servers should have the same amount of stores and they should all have the same exchange prefixes.  For AR or HA scenarios all exchange paths must also be identical. 
  2. Another way to resolve a prefix mismatch for exchange is to use adsiedit.msc from the run line and manually change the prefixes to match. 
  1. Go to start, run and type adsiedit.msc
  2. once the gui opens right click in the top left on ADSI Edit and choose 'connect to' then when the box comes up change the 'select a well known naming context:' drop down to 'configuration'.
  1. Then drill down to the 'databases' bin by following the following screenshot:
  3. You should then see your stores on the right hand pane.  If you right click on a store and go to properties a box will come up.  If you scroll down to 'msExchESEParamBaseName' this is the exchange prefix.  You can click 'edit' and change the prefix manually so that the prefixes for the stores on the replica match the prefixes for the stores on the master.
  4. Once you have manually changed the prefix to match the other server click apply, then ok, then close adsi edit.
  3. You can then go back to the RHA manager now that the prefixes all match and run auto discovery if you made any  changes to the master stores.  If only the replica stores were changed     you should be able to just run the scenario to make sure the mismatch error is now gone.
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