Ingres 9.2 Migration Guide - Actian

Large Cache SupportLarge Cache SupportIn Ingres II 2.5, the total number of pages in all caches has been revised froman un-enforced limit of 65536 to 2**32-1. Ingres II 2.5 supports a 4 GBcache.In previous releases, when those pages belonging to a specific table needed tobe located, the buffer manager sequentially searched every buffer in everycache to find them. Even in installations with small caches, this was anexpensive operation, especially in those frequent instances in which there wereno table-pages in any cache. This operation occurred, for example, when atable's TCB was about to be released, typically when all referencingtransactions had no immediate need to use the table. Delays caused by thisoperation could show up in unexpected situations, such as the use ofstatement level rules.In Ingres II 2.5, a cross-cache table hash queue has been added to the buffermanager to which pages are added as they are faulted in and removed whenthey are tossed. Thus, when the need to know a table's pages arises, a hashon the table's database ID and table ID is made and that list searched formatching pages. This change results in a significant decrease in the number ofcache pages visited and is most dramatic in installations configured with verylarge or multiple caches.Features Introduced in Ingres II 2.5 211