Browse Prior Art Database

DBMS PROTOCOL FOR SAFE FILE EXTENSION IN A MULTISYSTEM SHARED DISK ENVIRONMENT

IP.com Disclosure Number: IPCOM000014745D
Original Publication Date: 2001-Apr-01
Included in the Prior Art Database: 2003-Jun-20

Publishing Venue

IBM

Abstract

This invention describes a protocol which a DBMS follows in a multisystem shared disk environment to extend a file in such a way that a reader in one system would not miss reading any new data records which could be inserted by another system. During file extension the read/insert/update operations for the data records are not quiesced. The protocol also provides high availability since the failure of the system extending the file does not prevent a transaction in another system in the complex from extending the file and continuing with its insert of data record. A single system DBMS, such as DB/2, tracks the high-water mark (hwm) of the file space in a file control structure (FCS). This is used by the DBMS for the following purposes: 1. The Buffer manager component disallows any reads beyond the hwm since there is no valid data beyond that point. 2. When the data manager component of the DBMS determines that there is no room to inset a data record in the file space, it requests the Buffer manager for a new page number which is