Wem upgrade from 1912 to 2112 fails with below error:

1.Run the following queries on the wem database select * from VUEMSystemUtilities where name='AppLockerControllerReplaceModeOn'; //legacy data select * from VUEMSites; //site list
2. Find sites which are in the site list, but its id does not exist in the legacy data list.
3. Fix the partial data with the following statement: insert into VUEMSystemUtilities (IdSite, Name, Type, Value, State, RevisionId) values (TOKEN_SITE_ID, 'AppLockerControllerReplaceModeOn', 1,1,1,1)
4. Tried the DB update again and upgrade was successful.

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Problem Cause

While upgrading from 1912 to 2112, it will migrate legacy setting to a new place and the legacy settings are created when we create site, so there maybe some issues which cause the site to create partially and cause the data to be incorrect