The three configuration parameters that control the total number of databases, indexes, and objects that can be open at one time are managed by special caches called metadata caches. The metadata caches reside in the kernel and server structures portion of Adaptive Server memory. You configure space for each of these caches with these parameters:
When Adaptive Server opens a database or accesses an index or an object, it needs to read information about it in the corresponding system tables: sysdatabases, sysindexes, and sysobjects. The metadata caches for databases, indexes, or objects let Adaptive Server access the information that describes it in the sysdatabases, sysindexes, or sysobjects row directly in its in-memory structure. This improves performance because Adaptive Server bypasses expensive calls that require disk access. It also reduces synchronization and spinlock contention when Adaptive Server has to retrieve database, index, or object information at runtime.
Managing individual metadata caches for databases, indexes, or objects is beneficial for a database that contains a large number of indexes and objects and where there is high concurrency among users. For more information about configuring the number of metadata caches, see “number of open databases”, “number of open indexes”, and “number of open objects”.
