Ensure the SQL Server login associated with the database user has been added to the instance under Security > Logins, prior to running the sp_change_users_login stored procedure.When starting the service, the ‘SDE’ user is the only user required. This also must be run for any SQL Server authenticated database users that own data. This should be run against all databases in which the ‘SDE’ user requires access to manage the database. The stored procedure (SP_CHANGE_USERS_LOGIN) can be run to correct this problem by mapping an existing database user to their corresponding SQL Server login.

If the SDE login is not added and synched with the user within that database, the connection fails with Bad Login User or the service does not start. In these scenarios, the SDE user within the geodatabase is not in synch with the login for that instance of SQL Server. This process is always required when an SDE schema database is restored from a backup (.bak), or attached from a previously detached database (.mdf). Instructions provided describe how to re-synch SQL Server logins with the database users after restoring a database from backup. How To: Re-synch SQL Server logins or users after restoring a database from backup Summary

Sql repair master database