Record locking is a capability which is required for many applications, notably, for database applications. Many file system implementations support either advisory record locking and/or mandatory record locking. With advisory record locking, an application must check to see if a record is locked before performing an operation on the record. Using advisory record locking, if an application accesses a locked record, the operation is permitted with no indication from the implementation that a lock was violated. This is in contrast to mandatory record locking where locks are enforced by the implementation. Using mandatory record locking, an application which attempts to violate a lock is refused access an error condition. In IEEE 1003.1-1990, record locking is advisory.
A record locking capability on either a local or a remote file system requires a file system implementation more complex than one that just provides input/output to files. For this reason and for performance considerations, many file system implementations do not provide record locking. For a remote file system, a record locking capability requires support from the client implementation, the server implementation, and the protocol. One of the goals of transparent file access is for a client to be able to have access to as many remote file systems as possible even if the access provided does not support all of the capabilities of the client file system. This implies that even if the client implementation supports record locking, that client may be accessing a server which cannot support record locking and/or may be accessing a server using a protocol which does not support record locking. In the case of a client using IEEE 1003.1-1990, not only must the server and the protocol support record locking, but the server and the protocol must support advisory record locking.