Sharing Of Disk Files Without Locking
Original Publication Date: 1979-Dec-01
Included in the Prior Art Database: 2005-Feb-20
When two or more processes access the same data set on a disk file, there is the possibility that the same physical record may be accessed and written by more than one of them in a sequence that will destroy what another process has done. This is called inadvertent overwrite. The problem is usually solved by each process locking every record it reads in anticipation of writing it back. Later, after the record has been either updated or processed without updating, the lock is released. Locking prevents and protects other processes from reading a particular record until the first process has relinquished control of the record. However, there are several problems that locking introduces. There are some sequences that may cause processes to become embraced in a deadlock.