File "restore_symboltable" created after successful restore

Hi 

I've restored successfully from archive some data to a NetApp location (working with NDMP) and noticed that a file called "restore_symboltable" was created with owner root: -rw-------   1 root     root     30072832 Feb 21 18:20 restore_symboltable

Any idea what this file might be and do I need it ? I've done many restores overs the years and never seen this file.

Thanks