Symptoms

After moving K2 DB (or non-consolidated set of K2 DBs) onto new SQL server or server instance and reconfiguring of K2 blackpearl K2 still keeps hardcoded values in the AuthInit and RoleInit fields for the K2 SQL User Manager security label which refer to old SQL Server instance. If this instance taken offline K2 service fails to start till these entries updated with values pointing to new SQL service instance.
 

Diagnoses

This is expected behavior as SQL UM label is being added manually it is also expected to be maintained in up-to-date state manually. This is similar to additional domains connectivity configuration which is being performed post K2 installation - once you run reconfigure only primary domain remains and you have to re-add additional domains manually. Logic here is that whatever has been configured outside of setup manager has to be maintained manually as it is not being covered by K2 setup manager. For this specific issue there is an existing feature request (internal ID 690851) to consider possibility of handling/updating this automatically so that when K2 database is restored to a different SQL server/instance and K2 is reconfigured to use it, the AuthInit and RoleInit fields for the K2 SQL UM security label updated with the new SQL server/instance information.
 

Resolution

Update the AuthInit and RoleInit fields for the K2 SQL UM security label manually. I.e. you have to edit oK2HostServer].edbo]..SecurityLabels] table and update entry with SecurityLabelName = 'K2SQL' so that it contains name of the new SQL server in vAuthInit] and tRoleInit] columns.