Oracle architecture and backup (15th) bg-lgwr

I. What is the LGWR write condition for the LGWR process: the size of logs that are fully occupied at the time of submission reaches 1 m, and Thelogwriterprocesswritesredologentriestodisk. Digest (SG

I. What is The LGWR write condition for The LGWR process: The size of The logs reaches 1/3 at The time of submission and reaches 1 M every three seconds before The DBWn process writes The log writer process writes redo logentries to disk. redo log entries are generated in the redo log buffer of thesystem global area (SG

1. What is an LGWR process?

LGWR write conditions:

When submitting

1/3 full

The log size reaches 1 MB.

Every three seconds

Before DBWn Process Writing

The log writer process writes redo logentries to disk. redo log entries are generated in the redo log buffer of thesystem global area (SGA ). LGWR writes the redo log entries sequentially into aredo log file. if the database has a multiplexed redo log, then LGWR writes theredo log entries to a group of redo log files.

Example 2

[Oracle @ localhost desktop] $ ps-ef | grep ora _ | grep lgworacle 6446 1 0? 00:00:00 ora_lgwr_orcl [oracle @ localhost desktop] $ kill-9 6446 [oracle @ localhost desktop] $ ps-ef | grep ora _ | grep lgw [oracle @ localhost desktop] $ ps-ef | grep ora_oracle 6486 2720 0 00:00:00 pts/0 grep ora _ [oracle @ localhost desktop] $ sqlplus/as sysdba; SQL * Plus: Release 10.2.0.1.0-Production on Thu Jun 6 11:17:45 2013 Copyright (c) 1982,200 5, Oracle. all rights reserved. connected to an idle instance. SQL> s TartupORACLE instance started. total System Global Area 838860800 bytesFixed Size 1222192 bytesVariable Size 788531664 bytesDatabase Buffers 46137344 bytesRedo Buffers 2969600 bytesDatabase mounted. database opened. SQL> show parameter log_buff; NAME TYPE VALUE -------------------------------------- log_buffer integer 2923520SQL> exit; Disconnected from Oracle Dat Abase 10g Enterprise Edition Release 10.2.0.1.0-ProductionWith the Partitioning, OLAP and Data Mining options [oracle @ localhost desktop] $ ps-ef | grep ora _ | grep lgworacle 6499 1 0 11: 17? 00:00:00 ora_lgwr_orcl [oracle @ localhost desktop] $ ps-ef | grep ora_oracle 6491 1 0? 00:00:00 ora_pmon_orcloracle 6493 1 0? 00:00:00 ora_psp0_orcloracle 6495 1 0? 00:00:00 ora_mman_orcloracle 6497 1 0? 00:00:00 ora_dbw0_orcloracle 6499 1 0? 00:00:00 ora_lgwr_orcloracle 6501 1 0? 00:00:00 ora_ckpt_orcloracle 6503 1 0? 00:00:00 ora_smon_orcloracle 6505 1 0? 00:00:00 ora_reco_orcloracle 6507 1 0? 00:00:00 ora_cjq0_orcloracle 6509 1 0? 00:00:00 ora_mmon_orcloracle 6511 1 0? 00:00:00 ora_mmnl_orcloracle 6513 1 0? 00:00:00 ora_d000_orcloracle 6515 1 0? 00:00:00 ora_s000_orcloracle 6519 1 0? 00:00:00 ora_qmnc_orcloracle 6525 1 0? 00:00:00 ora_j000_orcloracle 6527 1 0? 00:00:00 ora_q000_orcloracle 6529 1 0? 00:00:00 ora_q001_orcloracle 6535 2720 0 00:00:00 pts/0 grep ora _

Summary

1. LGWR writes the redo logs to the redo log file in sequence.

2. LGWR write conditions: at the time of submission, it reaches 1/3 full, the log size reaches 1 M, every three seconds, before the DBWn process writes.

3. Log buffer: writes data to logfile through the LGWR process.

4. Run the ps command in Linux to view the process.

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