Oracle Corp’s 64-bit Very Large Memory option will enable existing 32-bit applications to take advantage of the raw performance power on Digital Equipment Corp’s AlphaServers running 64-bit Digital Unix. It will roll onto other 64-bit architectures as they appear. Very Large Memory includes two components, Large System Global Areas, LSGAs and Big Oracle Blocks, BOBs. The former increase the amount of database buffer cache that can be addressed way beyond the 4Gb possible on existing 32-bit systems. Indeed DEC believes Very Large Memory will be able to take advantage of systems it expects to follow with upwards of 50Gb RAM, when 64M-bit dynamic RAMs eventually ship. The performance of databases is directly related to the amount of the database that’s cached in memory, the object being to avoid processor time consumption and, therefore, costly input-output transactions. Large System Global Areas uses as much memory as it can to cache database blocks: ideally an entire database would be mapped from disk into main memory. Large System Global Areas is transparent to applications, so the code does not have to be changed. Big Oracle Blocks enable blocks of data up to 32Kb in size to be transferred in each input-output operation, up from the 2Kb allowed by 32-bit systems, or 8Kb under existing 64-bit architectures. Very Large Memory is suited to operations that use the same data sets repeatedly, full table scans and few input-outputs.
