Data base recovery in shared disks and client-server architectures

Solutions to the problem of performing recovery correctly in shared-disks (SD) and client-server (CS) architectures are presented. In SD, all the disks containing the data bases are shared among multiple instances of the database management system (DBMS). In CS, the server manages the disk version of the data base. The clients, after obtaining database pages from the server, cache them in their buffer pools. Clients perform their updates on the cached pages and produce log records. In write-ahead logging (WAL) systems, a monotonically increasing value called the log sequence number (LSN) is associated with each log record. Every database page contains the LSN of the log record describing the most recent update to that page. This is required for proper recovery after a system failure. A technique for generating monotonically increasing LSNs in SD and CS architectures without using synchronized clocks is presented.<
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