Oracle Database server structures:
1.memory structures
2.process structures
3.stroage structures
Oracle Database system:
1.Oracle Database
2.database instance
•System Global Area(SGA)
•Shared Pool : Caches various constructs that can be shared among users
- Library cache
- Shared SQL area
- Data dictionary cache
- Control structures
•Database buffer cache :Caches blocks of data retrieved from the database
Is part of the SGA
Holds copies of data blocks that are read from data files
Is shared by all concurrent users
•KEEP buffer pool : A specialized type of database buffer cache that is tuned to retain blocks of data in memory for long periods of time
•RECYCLE buffer pool : A specizlied tyoe of database buffer cache that is tuned to recycle or remove block from memory quickly
•nK buffer cache : One of several specialized database buffer caches designed to hold block size different than the default database block size
•Redo log buffer : Caches redo information(used for instance recovery) until it can be written to the physical redo log files stored on the disk
Is a circular buffer in the SGA
Holds information about chages made to the database
Contains redo entries that have the information to redo chages made by operations such as DML and DLL
•Large pool : Optional raea that provides large memory allocations for certain large process,such as Oracle backup and recovery operations,and I/O server process
Session memeory for the shared server and the Oracle XA interface
I/O server processes
Oracle Database backup and restore operations
•Java pool : Used for all session-specific java code and data in the Java Virtual Machine(JVM)
Java pool memory is used to store all session-specific Java code and data in the JVM
•Stream pool : Used by Oracle Streams to stroe information required by capture and apply
Streams pool memory is used exclusively by Oracle Streams to:
- Store buffered queue messages
- Provide memory for Oracle Streams processes
• Global Area Program (PGA)
•stack space
• user global area (UGA)
Cursor area for storing runtime information about a session
User session data storage area for control information about session
SQL working areas for processing SQL statements consiting of :
- A sort area for functions that order data such as ORDER BY and GROUP BY
- A hash area for performing hash joins of tables
- A create bitmap area used in bitmap index creatiion common to data warehouses
- A bitmap merge area used for resolving bitmap index plan execution