A System.OutOfMemoryException triggered within SureSync indicates that your system is low on memory. It is recommended to look at Task Manager on the Processes tab to make a determination about what is consuming memory.
SureSync 9 runs all components in 64-bit mode and uses a SQL database. You should rarely ever see a System.OutofMemoryException unless there is a true memory shortage on the machine running your Jobs.
SureSync 8 and SureSync 7
SureSync 8 and SureSync 7 can run an Access or a SQL database. By default, it will use an Access database. An Access database cannot be accessed by a 64-bit process, so SyncFiles.exe will run in 32-bit mode in this scenario. A 32-bit process can consume no more than 2GB of RAM. If the Root Paths being synchronized by the Job contain a large amount of files in single folder, this can cause a System.OutOfMemoryException error. When SureSync is scanning, it must load the entire contents of the listing of a particular directory into memory temporarily. If that list causes the SyncFiles.exe to hit 2GB, you will receive this error.
You can run SyncFiles.exe in 64-bit mode in these versions. First, you must move to a SQL database. Please see the Upgrading from Access to SQL article for further details.
Once the database is SQL, you can click on the Options tab of a Schedule or Real-Time Monitor and select the "Run job in 64-bit mode (uses more memory)" option. Stop and start the Schedule or Monitor for the change to take effect.