oracle architecture

76. Name the ORACLE Background Process ?

DBWR - Database Writer.

LGWR - Log Writer

CKPT - Check Point

SMON - System Monitor

PMON - Process Monitor

ARCH - Archiver

RECO - Recover

Dnnn - Dispatcher, and

LCKn - Lock

Snnn - Server.

77.  What Does DBWR do ?

Database  writer  writes  modified blocks from the database buffer cache to the data files.

78.When Does DBWR write to the database ?

DBWR  writes  when  more  data  needs  to  be read into the SGA and too few database  buffers  are free. The least recently used data is written to the data files first. DBWR also writes when CheckPoint occurs.

79. What does LGWR do ?

Log  Writer (LGWR) writes redo log entries generated in the redo log buffer of the SGA to on-line Redo Log File.

80. When does LGWR write to the database ?

LGWR   writes  redo  log  entries  into  an  on-line  redo  log  file  when transactions commit and the log buffer files are full.

81. What is the function of checkpoint(CKPT)?

The  Checkpoint  (CKPT)  process  is  responsible  for  signaling  DBWR  at checkpoints  and  updating  all  the  data  files  and control files of the database.

82. What are the functions of SMON ?

System  Monitor (SMON)  performs instance recovery at instance start-up. In a multiple instance system (one that uses the Parallel Server), SMON of one instance  can  also  perform instance recovery for other instance that have failed SMON also cleans up temporary segments that are no longer in use and recovers  dead  transactions  skipped  during  crash  and instance recovery because of  file-read or off-line errors. These transactions are eventually recovered  by SMON when the tablespace or file is brought back on-line SMON also  coalesces  free  extents  within  the  database  to  make  free space contiguous and easier to allocate.

83.  What are functions of PMON ?

Process Monitor (PMON)  performs process recovery when a user process fails PMON  is  responsible  for cleaning up the cache and Freeing resources that the  process  was using PMON also checks on dispatcher and server processes and restarts them if they have failed.