When creating a new feature dataset or feature class in a file geodatabase located on a network drive, an error is returned indicating that the file is locked even though only one user is accessing the file. While this issue was originally reported through feature dataset and feature class creation, any schema change that creates new files in the file geodatabase may encounter this behavior.
Some anti-virus programs running on the network have been identified as part of this problem. This can result in locking issues between the anti-virus software and ArcGIS. Some anti-virus programs scan newly created files on creation. This can result in locking issues. Anti-virus programs known to cause this problem include BitDefender and Etrust. Review the issue, in general, with an RDBMS. Refer to Microsoft: How to choose antivirus software to run on computers that are running SQL Server for more information.