tailieunhanh - Sizing the Shared Pool

Defined by SHARED_POOL_SIZE Library cache contains statement text, parsed code, and execution plan. Data dictionary cache contains definitions for tables, columns, and privileges from the data dictionary tables. UGA contains session information for Oracle Shared Server users when a large pool is not configured. | Sizing the Shared Pool Objectives After completing this lesson, you should be able to do the following: Determine the size of an object and pin it in the shared pool Tune the shared pool reserved space Describe the user global area (UGA) and session memory considerations Measure the library cache hit ratio List other tuning issues related to the shared pool Measure the dictionary cache hit ratio Set the large pool Shared Pool Contents Major components of the shared pool are: Library cache Data dictionary cache User global area (UGA) for shared server sessions Database buffer cache Redo log buffer Shared pool Library cache Data dictionary cache User global area Large pool UGA Shared Pool Contents The shared pool contains the following structures: The library cache, which stores shared SQL and PL/SQL code The data dictionary cache, which keeps information about dictionary objects The user global area (UGA), which keeps information about shared server connections when the large pool is not configured. Tuning Considerations for the Shared Pool A cache miss on the data dictionary cache or library cache is usually more expensive than a miss on most other SGA memory structures; therefore tuning the shared pool is a priority. When you tune the shared pool, you should concentrate on the library cache because the algorithm that assigns memory space in the shared pool prefers to hold dictionary data in memory longer than library cache data. Therefore, tuning the library cache to an acceptable cache hit ratio ensures that the data dictionary cache hit ratio is also acceptable. If the shared pool is too small, the server must dedicate resources to managing the limited space available. This consumes CPU resources and causes contention. If the shared pool is too large performance can decrease because: There is less memory for other memory structures (thus reducing performance) Many entries can make finding current contents slower than in a smaller pool. Shared Pool Defined by . | Sizing the Shared Pool Objectives After completing this lesson, you should be able to do the following: Determine the size of an object and pin it in the shared pool Tune the shared pool reserved space Describe the user global area (UGA) and session memory considerations Measure the library cache hit ratio List other tuning issues related to the shared pool Measure the dictionary cache hit ratio Set the large pool Shared Pool Contents Major components of the shared pool are: Library cache Data dictionary cache User global area (UGA) for shared server sessions Database buffer cache Redo log buffer Shared pool Library cache Data dictionary cache User global area Large pool UGA Shared Pool Contents The shared pool contains the following structures: The library cache, which stores shared SQL and PL/SQL code The data dictionary cache, which keeps information about dictionary objects The user global area (UGA), which keeps information about shared server connections when the large pool is .