Our customer reported today that Data Sync failed is failing with the following inner exception: System.OutOfMemoryException error. Sync failed with the exception 'An unexpected error occurred when applying batch file C:\\XXX\\XXXX\\AppData\\Local\\Temp\\XXX\\sync_zyz\\ec53ddeb-xxxx.batch. See the inner exception for more details.Inner exception: Exception of type 'System.OutOfMemoryException' was thrown. For more information, provide tracing ID ‘XXX9’ to customer support.'
This issue occurs because previous versions of Data Sync Agent was 32 bit application that can only address up to 2GB of memory in user mode, raising this error you when this limit is reached.
The suggestion for Data Sync Agent version is to install the version 64 bits downloading the latest one from here. You need to uninstall the x32 sync agent, install the x64 one, and re-submitting the agent key. The whole process is like migrating to sync agent 2.0.