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发布时间:2007-08-02 20:45:13

以前总有一个疑问,在什么情况下,才会出现,还没有commit,就已经将数据从data buffer写到数据文件上的情况?顺道记一下checkpoint产生的情况。[@more@]1、在commit前有cheakpoint发生2、data buffer 不够用时暂时想到这么多。checkpoint会刷新脏数据,但什么时候会发生checkpoint呢?以下几种情况会触发checkpoint。1.当发生日志组切换的时候2.当符合LOG_CHECKPOINT_TIMEOUT,LOG_CHECKPOINT_INTERVAL,FAST_START_IO_TARGETFAST_START_MTTR_TARGET参数设置的时候*13.当运行ALTER SYSTEM SWITCH LOGFILE的时候4.当运行ALTER SYSTEM CHEC......【阅读全文】

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发布时间:2007-08-02 20:24:04

oracle中经常会考到的几个状态,invalid,obsolete,expired,stale等等。自己试着总结一下[@more@]1、If one of the online redo log members is lost,the status in v$logfie will be INVALID 2、If the contents of the redo log file are incomplete ,the status of the file in the V$LOGFILE view will be STALE3、You are using RMAN to perform backup and recovery on your database.The backup of one of the files was lost because it was located on a failed media.If you use CROSSCHECK command to verify the existence of ......【阅读全文】

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发布时间:2007-08-01 22:33:28

似乎有一个oracle 原厂培训的机会...[@more@]昨天还和阿春谈起,想考oracle的OCP认证,需要一门oracle原厂培训。今天,机会就来了。本来是要给阿春去的,不过阿春又一个oracle adminstrator 1的培训了,他把这个培训让给我了。不知道领导会不会安排我去,如果能搞定这次培训,OCP就不是问题了。......【阅读全文】

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发布时间:2007-08-01 22:24:30

RMAN是不备份online redo log的。这个问题一直比较困惑,难道online redo log不需要备份?确实是的[@more@]看下面这段Avoiding the Backup of Online Redo LogsAlthough it may seem that you should back up online redo logs along with the datafiles and control file, this technique is dangerous. You should not back up online redo logs for the following reasons:* The best method for protecting the online logs against media failure is by multiplexing them, that is, having multiple log members in each group, on ......【阅读全文】

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发布时间:2007-08-01 21:14:45

Optimizer statistics are a collection of data that describe more details about the database and the objects in the database. These statistics are used by the query optimizer to choose the best execution plan for each SQL statement. [@more@] Optimizer statistics include the following:Table statisticsNumber of rowsNumber of blocksAverage row lengthColumn statisticsNumber of distinct values (NDV) in columnNumber of nulls in columnData distribution (histogram)Index statisticsNumber of leaf blocksLev......【阅读全文】

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