DWSYSTEM : DWTASKS table

In the process of migrating a Fortis customer to DocuWare (v6.12) using the "migration tool", approx. 1.5 million documents. I have noticed the database = dwsystem, table = dwtasks is rather large and does not seem to be reducing in size. It is currently 7.7 GB, with 10,602,091 records.

Why is this table so large? Will it eventually shrink over time or is this historical data that needs to be kept?

Please advise. Thank you

Is there a criteria in which records can be removed from the table?

I had this same issue and reviewed the records in the table and found a large number of them were not associated to Filecabinet GUIDS that existed. I am not certain but this seems to cause some issues with the way the tasks are removed from the table. I did a search of all the GUIDS in the settings and found the Task_Type 0 records that existed and deleted them. Once I did this the table started to shrink immediately. I did find you cannot remove the Task_Type=2 records as they are locked.  I have noticed that this also causes an issue with Backups.  All of the Docuware Backups I have failed with an error calling out the DWTask table. 
1) Exception Information

     Exception Type: DocuWare.Common.Exceptions.DWException
    MachineName: IL084PDW2
    CreatedDateTime: 11/12/2020 10:02:10 AM
    AppDomainName: DWAuthenticationServer.exe
    ThreadIdentityName: 
    DWUserLogLevel: Unknown
    TranslatedMessage: General error while reading data from table DWTasks
    Message: General error while reading data from table DWTasks
    TargetSite: Error accessing exception member - Exception has been thrown by the target of an invocation.
    HResult: -2146232832
There are currently over 6 million items in this table.  

I am hopeful reducing the number of records in this table will allow the backups to function or at very least help me to find the issues that still exist.