If you are using the CRM Outlook client you will find two sets of tables in the CRM database beginning with: SubscriptionStatistics and SyncEntry.
Like the AsyncOperationsBase table containing old and useless information, these tables present the same sorts of issues.
Luckily, the Microsoft UK Dynamics Support team has an answer:
There are some slight modifications to make the script run better, as outlined in an article from Customer Effective on the same subject:
Again, this is a SQL operation so if you are not comfortable with SQL, the please find someone who is.