Shared memory region accessed by all background processes and user processes. Contains components like Database Buffer Cache (for data blocks), Redo Log Buffer (for transaction redo information), Shared Pool (for SQL parsing and execution plans), and Large Pool (for large operations).
PGA (Program Global Area): Private memory region for each server process handling a user connection. Contains sort areas, hash areas, and session-specific data.
DBWn (Database Writer): Writes modified data blocks from the buffer cache to data files.
LGWR (Log Writer): Writes redo log entries from the redo oman phone number list log buffer to redo log files.
PMON (Process Monitor): Cleans up failed processes.
SMON (System Monitor): Performs crash recovery and temp segment cleanup.
CKPT (Checkpoint): Updates control file and data file headers during checkpoints.
ARCH (Archiver): Archives filled redo log files.
Logical vs. Physical Structure: Oracle separates the logical structure (tablespaces, segments, extents, data blocks) from the physical storage (data files). This abstraction allows for flexible storage management.