Oracle PGA vs SGA: Memory Structures Explained
In Oracle database, PGA (Program Global Area) and SGA (System Global Area) are two important memory structures within a database instance.
- PGA (Program Global Area): PGA is a private memory area for each database session, used to store session-level memory structures and data. PGA includes sorting area, session area, cursor area, etc. It is a memory area managed by each database session, storing data and memory required for session-level operations.
- SGA (System Global Area) is a shared memory area for the entire database instance, used to store database instance-level memory structures and data such as buffer cache, shared pool, and redo log buffer.
In general, PGA is a private memory area for each session, used to store session-level data and operations; whereas SGA is a shared memory area for the entire database instance, used to store instance-level data and operations. PGA and SGA together form Oracle’s memory management mechanism.
