一 什么是lgwr进程 lgwr写的条件： 提交的时候 达到三分之一满 日志的大小达到1m 每隔三秒 在dbwn进程写之前 the log writer process writes redo logentries to disk. redo log entries are generated in the redo log buffer of thesystem global area (sg
一 什么是lgwr进程 
        lgwr写的条件：
        提交的时候
        达到三分之一满
        日志的大小达到1m
        每隔三秒
        在dbwn进程写之前
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.
二 操作示例
[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgworacle 6446 1 0 11:15 ? 00:00:00 ora_lgwr_orcl[oracle@localhost 桌面]$ kill -9 6446[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgw[oracle@localhost 桌面]$ ps -ef | grep ora_oracle 6486 2720 0 11:17 pts/0 00:00:00 grep ora_[oracle@localhost 桌面]$ sqlplus / as sysdba;sql*plus: release 10.2.0.1.0 - production on thu jun 6 11:17:45 2013copyright (c) 1982, 2005, oracle. all rights reserved.connected to an idle instance.sql> startuporacle 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 database 10g enterprise edition release 10.2.0.1.0 - productionwith the partitioning, olap and data mining options[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgworacle 6499 1 0 11:17 ? 00:00:00 ora_lgwr_orcl[oracle@localhost 桌面]$ ps -ef | grep ora_oracle 6491 1 0 11:17 ? 00:00:00 ora_pmon_orcloracle 6493 1 0 11:17 ? 00:00:00 ora_psp0_orcloracle 6495 1 0 11:17 ? 00:00:00 ora_mman_orcloracle 6497 1 0 11:17 ? 00:00:00 ora_dbw0_orcloracle 6499 1 0 11:17 ? 00:00:00 ora_lgwr_orcloracle 6501 1 0 11:17 ? 00:00:00 ora_ckpt_orcloracle 6503 1 0 11:17 ? 00:00:00 ora_smon_orcloracle 6505 1 0 11:17 ? 00:00:00 ora_reco_orcloracle 6507 1 0 11:17 ? 00:00:00 ora_cjq0_orcloracle 6509 1 0 11:17 ? 00:00:00 ora_mmon_orcloracle 6511 1 0 11:17 ? 00:00:00 ora_mmnl_orcloracle 6513 1 0 11:17 ? 00:00:00 ora_d000_orcloracle 6515 1 0 11:17 ? 00:00:00 ora_s000_orcloracle 6519 1 0 11:17 ? 00:00:00 ora_qmnc_orcloracle 6525 1 0 11:18 ? 00:00:00 ora_j000_orcloracle 6527 1 0 11:18 ? 00:00:00 ora_q000_orcloracle 6529 1 0 11:18 ? 00:00:00 ora_q001_orcloracle 6535 2720 0 11:18 pts/0 00:00:00 grep ora_
三 总结 
        1.lgwr，将重做日志有序地写入重做日志文件中。
        2.lgwr写的条件：提交的时候、达到三分之一满、日志的大小达到1m、每隔三秒、在dbwn进程写之前。
        3. log buffer：通过lgwr进程写入到logfile中。
        4.linux中同样使用ps命令查看进程。
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