The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 10: Integrating FILESTREAM with other SQL Server Featureswith the modified value. The old file stays around in the FILESTREAM data containeruntil the garbage collector steps in and deletes it.Every FILESTREAM operation is linked to an LSN in the database transaction log. Thegarbage collector will remove a file marked for garbage collection only when the transactionlog is truncated past the LSN that created the FILESTREAM garbage file.When a FILESTREAM database is published, the transaction log cannot be truncated untilthe replication log reader agent reads the information from the transaction log. This candelay the FILESTREAM garbage collection, because the garbage collector cannot deletethe files until the transaction log is truncated.It is therefore possible that you will notice FILESTREAM garbage files lying around for alonger period if the FILESTREAM columns are replicated and the replication log readeragent does not run frequently.FILESTREAM and synchronization methodsIt is important to note that, if a publication includes tables having FILESTREAM columns,the snapshot synchronization methods offered by SQL Server Enterprise Edition cannotbe used.SQL Server Enterprise Edition provides two efficient synchronization methods forbuilding the replication snapshot, namely database snapshot and database snapshotcharacter, which generates the snapshot based on a database snapshot, resulting in nolocks being applied on the tables when the replication snapshot is being created. Databasesnapshots cannot include FILESTREAM filegroups (explained later in this chapter) andtherefore, if the publication includes FILESTREAM columns, snapshot synchronizationmethods are not supported.366