Home
AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Administrator's GuideThe HCL OneDB™ Administrator's Guide provides the information required to administer HCL OneDB™.
Disk, memory, and process management
Shared memoryThese topics describe the content of database server shared memory, the factors that determine the sizes of shared-memory areas, and how data moves into and out of shared memory.
Virtual portion of shared memoryThe virtual portion of shared memory is expandable by the database server and can be paged out to disk by the operating system.
Data-distribution cacheThe database server uses distribution statistics generated by the UPDATE STATISTICS statement in the MEDIUM or HIGH mode to determine the query plan with the lowest cost.
Dictionary cacheWhen a session executes an SQL statement that requires access to a system catalog table, the database server reads data from the system catalog tables.

Dictionary cache

When a session executes an SQL statement that requires access to a system catalog table, the database server reads data from the system catalog tables.

The database server stores the catalog data for each queried table in structures that it can access more efficiently during subsequent queries on that table. These structures are created in the virtual portion of shared memory for use by all sessions. These structures constitute the dictionary cache.

You can configure the size of the dictionary cache with the DD_HASHSIZE and DD_HASHMAX configuration parameters. For more information about these parameters, see the chapter on configuration effects on memory in your HCL OneDB™ Performance Guide.