The Checkpoint and Log Writer Process

An Oracle process is a program that depending on its type can request information, execute a series of steps, or perform a specific task.

There are three types of processes in oracle database:

• User process: Started at the time a database user requests connection to the Oracle server.
• Server process: Connects to the Oracle Instance and is started when a user establishes a session.
• Background process: Available when an Oracle instance is started.

The Checkpoint(CKPT) is a background process and does the following tasks:

• It signals the database writer process (DBWn) at each checkpoint.
• It updates the data file headers with the checkpoint information.
• It updates the control files with the checkpoint information.

And the log writer (LGWR) process is also a background process is responsible for transferring the contents of the redo log buffer to the online redo log files.

The LGWR writes to the online redo files under the following conditions:

• at each commit
• Every three seconds
• When the redo log buffer is one-third full