VLM Capabilities of the Sybase System 11 SQL Server

Inc. coincided with the widespread availability and use of very large memory (VLM) technology on DIGITAL’s Alpha microprocessor-based computer systems. Technological features of the System 11 SQL Server were used to achieve record results of 14,176 transactions-per-minute C (tpmC) at $198/tpmC on the DIGITAL AlphaServer 8400 server product. One of these features, the Logical Memory Manager, provides the ability to fine-tune memory management. It is the first step in exploiting the semantics of database tables for better use of memory in VLM systems. To partition memory, a database administrator (DBA) creates multiple named buffer caches. The DBA then subdivides each named cache into multiple buffer pools for various I/O sizes. The DBA can bind a database or one table in a database to any cache. A new thread in the SQL Server engine, called the Housekeeper, uses idle cycles to provide free (nonintrusive) checkpoints in a large memory system. In this paper, we briefly discuss VLM technology. Then we describe the capabilities of the Sybase System 11 SQL Server that address the issues of fast access, checkpoint, and recovery of VLM systems, namely, the Logical Memory Manager, a VLM query optimizer, the Housekeeper, and fuzzy checkpoint.