Oracle的体系结构

进程架构：

1. Database Writer Process(DBWn):

Writes modified(dirty) buffers in the database buffer cache to disk:
a. Asynchronously while performing other processing

b. To advance the checkpoint

2. Log Writer Process(LGWR)

Writes the redo log buffer to a redo log file on disk

- When a user process commits a transaction

- When the redo log buffer is one-third full

- Before a DBWn process writes modified buffers to disk

- Every 3 seconds

3. Checkpoint Process (CKPT)

Records checkpoint information in:

Control file

Each data file header

4. System Monitor Process (SMON)

Performs recovery at instance startup

Cleans up unused temporary segments

5. Process Monitor Process(PMON)

a. Performs process recovery when a user process fails

- Cleans up the database buffer cache

- Frees resources that are used by the user process

b. Monitors sessions for idle session timeout

c. Dynamically registers database services with listeners

6. Recoverer Process

a. Used with the distributed database configuration

b. Automatically connects to other databases involved in in-doubt distributed transactions

c. Automatically resolves all in-doubt transactions

d. Removes any rows that correspond to in-doubt transactions

7. Archiver Processes (ARCn)

a. Copy the redo log files to a designated storage device after a log switch has occurred

b. Can collect transaction redo data and transmit that data to standby destinations

ITPub博客

Oracle进程架构