Symptoms
How to remove completed instances

Diagnoses
Customer wish to free up spaces in K2 SQL Server by removing completed Process Instances

Resolution
We have a archiving function to move those completed and stopped instances from K2 database to another Archive database. Here is the KB:-
http://help.k2.com/kb000322

Once the archiving has completed, customer will need to shrink the database to reduce the size of existing K2 database. Depend of the size of the K2 database, the archiving script could take a while to run and it could potentially causing performance issue during the archiving process. Hence, this operation should only be carried out after working hour.