When publishing modified pages, or performing synchronization, it is possible that you experience degrading performance during the process due to fragmented database space. Fragmented data can cause Microsoft SQL Server to perform unnecessary data reads and slow inserts of new data in the database, slowing down SQL Server’s performance.
Database GUIDs generation
Sitefinity stores GUIDs in the database with randomly generated primary key.
Randomly generated GUIDs help eliminate conflicts when more than one developer is working with the same code, but different local database.
When using random GUIDs, with time, your database can become fragmented. You should reorganize and rebuild the database index on regular intervals.
For more information, see Reorganizing and Rebuilding Indexes.
Rebuild database indexes
In addition, you can rebuild the database indexes to maintain the database and optimize its performance. Thus, when a new record is inserted and needs to be put between existing records, this does not cause fragmentation of the index. This is valid especially for the clustered primary key indexes which define the physical order of the database records.
You can either rebuild indexes manually or schedule scripts to do this on a regular basis. For more information see: Rebuild database indexes
NOTE: The rebuilding operation might take considerable time, depending on the size of your database.