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What is true about the background processes Dbwr and Lgwr?
Database Writer process (DBWR) writes buffers to datafiles. DBWR is an Oracle background process responsible for buffer cache management. of performing a checkpoint from other work performed by LGWR, the Log Writer process(LGWR). The Process Monitor (PMON) performs process recovery when a user process fails.
Where Lgwr process writes information?
Log Writer Process (LGWR) The log writer process (LGWR) is responsible for redo log buffer management—writing the redo log buffer to a redo log file on disk. LGWR writes all redo entries that have been copied into the buffer since the last time it wrote.
What are the situations when Dbwr and Lgwr will write?
The DBWn process writes dirty buffers to disk under the following conditions: When a server process cannot find a clean reusable buffer after scanning a threshold number of buffers, it signals DBWn to write. DBWn writes dirty buffers to disk asynchronously while performing other processing.
Why Lgwr writes before Dbwr?
Log writer process (LGWR) writes redo entries after certain amount of time to ensure that free space is available for new redo entries. The Log Writer (LGWR) writes contents from the Redo Log Buffer to the Redo Log File that is in use.
What is the difference between Smon and Pmon processes?
PMON and SMON are two required background processes. PMON is the Process Monitor which is responsible for recovering processes when the user process fails. PMON does the process cleanup. SMON is the System Monitor which is responsible for recovering the system after a failure.
What is Log_archive_max_processes?
LOG_ARCHIVE_MAX_PROCESSES specifies the number of archiver background processes (ARC0 through ARC9) Oracle initially invokes. If the LOG_ARCHIVE_START initialization parameter has the value true , then this value is evaluated at instance startup.
What is Oracle Archiver?
“Archiving” is defined as the operation in which the archiver background process copies filled online redo log files to offline destinations. An offline copy of an online redo log is called an archived redo log. You must operate the database in ARCHIVELOG mode to archive redo log files.
What are the responsibilities of Smon?
SMON (System MONitor) is an Oracle background process created when you start a database instance. The SMON process performs instance recovery, cleans up after dirty shutdowns and coalesces adjacent free extents into larger free extents. SMON wakes up every 5 minutes to perform housekeeping activities.
What is the purpose of Ckpt?
CKPT (Oracle Checkpoint Process) is an Oracle background process that timestamps all datafiles and control files to indicate that a checkpoint has occurred. The “DBWR checkpoints” statistic (v$sysstat) indicates the number of checkpoint requests completed.