The configuration parameters that control the total number of databases, indexes, partitions and objects that can be open at one time are managed by the metadata caches. The metadata caches reside in the server structures portion of Adaptive Server’s memory. You configure space for each of these caches with these parameters (For information about these parameters, see Setting Configuration Parameters in the System Administration Guide, Volume 1):
number of open databases
number of open indexes
number of open objects
number of open partitions
When Adaptive Server opens a database or accesses an index, partition, or object, it reads information about it in the corresponding system tables: The information for databases in in sysdatabases, the information for indexes in in sysindexes, the information for partitions is in syspartitions and so on.
The metadata caches for databases, indexes, partitions or objects allow Adaptive Server to access the information that describe them in sysdatabases, sysindexes, syspartitions or sysobjects 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, partition, or object information at runtime.Managing individual metadata caches for databases, indexes, partitions, or objects is beneficial for a database that contains a large number of indexes, partitions, and objects and where there is high concurrency among users.
