Dictionary Buffer (Oracle)

Use

You can use this procedure to display the dictionary buffer.

Procedure

Choose Tools →Administration →Computing Center →Management System →Control →Performance Menu →Database →Activity.
Alternatively, use transaction codeST04.
Choose Goto → Statistics → Row cache.

This screen displays in-depth statistics on the quality of the Oracle data dictionary buffer cache (row cache). Entries for all cache objects are displayed here.

This information is read into memory from the dictionary tables stored on disk. When an Oracle instance is first started, this cache is necessarily empty and must be loaded as dictionary information is accessed. For this reason, hit ratios are generally low at database instance startup time and stabilize over time.

Note

In version 6 of Oracle, there were init<SID>.ora parameters that could be changed if the values in Used were close to those in Total. This no longer the case with version 7. Instead, setting the data dictionary cache is an automatic process executed by the database itself. The only parameter you can use to control the data dictionary is shared_pool_size (SHARED_POOL_SIZE (Oracle)).

You can allocate more room in the shared pool by increasing the value of this parameter. As the data dictionary cache is part of the shared pool, if necessary it can dynamically extend itself within the shared pool area, as long as there is sufficient free memory space available.