Oracle Error Codes

cannot obtain string enqueue for datafile string

The file access enqueue could not be obtained for a file specified in a backup, copy or restore operation. If the enqueue type shown is shared, then the file is the input file for a backup or copy. If the type is exclusive, then the file is the output file for a datafile copy or restore which is attempting to overwrite the currently active version of that file – in this case, the file must be offline or the database must be closed. If the type is read-only, then you are attempting to back up or copy this file while the database is in NOARCHIVELOG mode.

How to Solve :

Wait until the conflicting operation is complete, then retry the copy or backup. If the database is in NOARCHIVELOG mode, then all files being backed up must be closed cleanly.