When you’ve moved an mailbox database, the old catalog data is still present on the old partition. This prevents deleting the specific partition. When you try to delete those files, you receive this error.

Error description:
The Catalog data folder stays in place after a database move path action. The folder couldn’t be cleaned up because it is in use by the Microsoft Exchange Search Indexing service

Solution:
First we have to temporarely disable the indexing on the particular mailbox database. Then we stop the indexing service of Exchange so we can delete the remaining files. The last step is to enable the indexing again.

Actions:
You can follow the next steps.

- Open the Exchange Management Shell and run the following command:
     Set-MailboxDatabase -Identity databasename -IndexEnabled $false
-Before moving / cleaning the catalog files, stop the service Microsoft Exchange Search Indexer
- Move the catalog files to the new database location or clean them up.
- Start the service Microsoft Exchange Search Indexer
- Open the Exchange Management Shell and run the following command:
Set-MailboxDatabase -Identity databasename -IndexEnabled $true