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Lesson 12

Understanding Oracle's Memory Architecture Conclusion


This module discussed how Oracle uses Sort Areas, shrinking and expanding them as necessary, depending on how much data there is to sort.
Now you should be able to:
  1. Describe the memory structures that make up the SGA
  2. Describe how the database buffer cache manages data blocks
  3. Describe the purpose of the three types of buffer pools
  4. Describe the function of the redo log buffer.
  5. Identify the function of the large pool
  6. Describe how each session gets its own memory
  7. Name the contents of the PGA.
  8. Describe how Oracle uses memory for sorting

Glossary

This module introduced you to the following terms:
  1. background processes
  2. dedicated server process:A database configuration in which a server process handles requests for a single client process.
  3. default buffer pool: Placing a table into the keep pool merely changes the part of the buffer cache where the blocks are stored. Instead of the blocks being cached in the default buffer pool, they are cached in the keep buffer pool. No separate algorithm is used to control keep pool caching.
  4. dirty list: The dirty list points to all the buffers that have been modified and that need to be written back to disk. Sometimes dirty buffers will be found in the LRU List as well, but eventually they too will make it to the dirty list.
  5. execution plan
  6. keep buffer pool: An alternate buffer pool where by convention you would assign segments that were accessed fairly frequently, but still got aged out of the default buffer pool due to other segments needing space.
  7. large pool: Optional area in the SGA that provides large memory allocations for backup and restore operations, I/O server processes, and session memory for the shared server and Oracle XA.
  8. Program Global Area: The Program Global Area (PGA) is a private memory region that contains the data and control information for a server process. Only a server process can access the PGA. Oracle Database reads and writes information in the PGA on behalf of the server process.
  9. parsing: The process of pulling apart a SQL statement and figuring out how best to execute it.
  10. PGA:
  11. recycle buffer pool: A pool of buffers in the database buffer cached used for that should be held in memory for the minimum amount of time possible.
  12. server process: A process on the server that communicates with a user process, and which processes SQL statements submitted by that user process.
  13. Sort Area: SORT_AREA_SIZE specifies (in bytes) the maximum amount of memory Oracle will use for a sort. After the sort is complete, but before the rows are returned, Oracle releases all of the memory allocated for the sort, except the amount specified by the SORT_AREA_RETAINED_SIZE parameter.
  14. System Global Area: In the database management systems developed by the Oracle Corporation, the System Global Area (SGA) forms the part of the system memory (RAM) shared by all the processes belonging to a single Oracle database instance. The SGA contains all information necessary for the instance operation.

Memory Architecture Definitions

Click the link below to read about memory architecture definitions that were covered for the most significant points in this module.
Memory Architecture Definitions
In the next module, you will prepare to create your first database.