Multi Access Data Sharing Facility Utilizing Magnetic Bubble Storage
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
This article describes two procedures for allowing multiple and concurrent programs and multiple hosts to access the same data at the record level. In accordance with the first procedure, a COMPARE/SWAP technique is employed which maintains a version number at the beginning of each record. Whenever a read and then updated record is to be rewritten by a first task, the version number is checked to assure that the record has not been updated by a second task since being read by the first task. In accordance with the second procedure, a LOCK/UNLOCK technique is employed which maintains a lock word at the beginning of each record. The lock word is inspected to determine which hosts are sharing the data, waiting to share, have exclusive control, or are waiting for exclusive control.