系列讲座(二).ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,ORACLE Database Concepts,Administration,系列讲座（二）,樊若蕻,数据库课题，计算中心 2003.4,基本概念复习,了解,oracle,的结构很重要，特别是从调试的角度，如果不知道,Oracle,是如何操作的，就不可能适当地调试一个,Oracle,数据库。,。,Oracle,使用内存方式,。,Oracle,使用磁盘文件方式和各类进程之间的互相作用方式,理解数据库和实例 1.数据库,在,Oracle,领域里，数据库指的是文件集合，这些文件用来存储管理相关数据。,一个,oracle,数据库由物理文件，内存区和进程组成。,数据库中的数据存储在磁盘上的物理文件中。数据被使用时，则吊入内存。,files：,不同类型,Database files:,.,数据文件:,datafiles,.,控制文件:,control files,.,重做日志:,redo log files,.,跟踪文件及警告日志:,trace files,alert files,files：,不同类型,Nondatabase,files:,.,参数文件:,parameter file,.,口令文件:,password file,1.1.,Data files:,Every Oracle database has one or more physical,datafiles,.The,datafiles,contain all the database data.,数据文件典型地代表了根据他们使用的磁盘空间和数量所决定的一个,Oracle,数据库的容积。,内容,：,。表数据,。索引数据,。数据字典定义,。回滚数据信息,。存储过程，函数和数据包的代码,。常用来排序的临时数据,由于性能原因，每一种类型的数据放在相应的一个或一系列文件中，将这些文件放在不同的磁盘中。,types:,.data dictionary .data,.redo data .index,.temporary data ,1.2,Control files:,存储有关数据库状态的信息,Oracle,建议应该镜像控制文件（2/3）,每一个控制文件的内容是完全相同的,控制文件内容：,。,数据库名,。表空间信息,。所有数据文件的名字和位置,。所有,redo,日志文件的名字和位置,。,当前的日志序列号,。检查点信息,。关于,redo,日志和归档的当前状态信息,Control file,控制文件把,Oracle,引导到数据库文件的其它部分。启动一个实例时，,Oracle,从参数文件中毒区控制文件的名字和位置。安装数据库时，,Oracle,打开控制文件。最终打开数据库时，,Oracle,从控制文件中读取数据文件的列表并打开其中的每个文件。,参数文件,控制文件,控制文件,日志文件,日志文件,数据文件,数据文件,每个控制文件的,内容是完全相同,指向控制文件,控制文件指向数据和日志文件,1.3,redo log files:,Every Oracle database has a set of two or more redo log files.,(1).Online redo log file:,循环使用,(2).,Archived redo log file(offline),1.4,Trace Files and Alert Files,Each server and background process can write to an associated trace file.,在,instance,中运行的每一个,background process,都有一个,trace file,与之相连。,Trace file,记载,background process,所遇到的重大事件的信息。,Alert file,The alert file is a special trace file.,Each database also has an Alert log.The Alert file of a database is a chronological log of messages and errors,1.5,Parameter files,包括大量影响,Oracle,数据库实例功能的摄制。,。,数据库控制文件的定位,。,Oracle,用来缓存从磁盘上读取的数据的内存数量,。,Oracle,用来缓存,SQL,语句的执行计划，,PL/SQL,过程和数据字典信息以便与它们不必从磁盘连续读取的内存的数量,。默认的优化程序的选择,Parameter files,和数据库文件相关，执行两个重要的功能：,1为数据库指出控制文件,2为数据库指出归档日志的目标,1.6,password file,The password file authenticates which users are permitted to start up and shut down an Oracle instance.,2.实例:,An Oracle instance is the combination of the background processes and memory structures,数据库实例是用来访问数据库文件集的存储结构及后台进程的集合,实例是一系列进程，他们一起运行来操作数据库。这些进程紧密地一起运行，共同访问内存中的一块区域.,2.1,System Global Area(SGA):,组成：,1 The share pool,(1).library cache：,.the shared SQL areas:A shared SQL area contains the parse tree and execution plan for a given SQL statement.,.PL/SQL:Oracle processes PL/SQL program units.,SGA:1shared pool,(2).data dictionary cache:is a collection of,the most recently used definitions in the,database.,It include Information about database files,tables,indexes,columns,users,privileges,and other database objects.,(3).buffers for parallel execution messages,SGA,2,The database buffer cache,Holds copies of data blocks read from,datafiles,.All user processes concurrently connected to the instance share access to the database buffer cache,SGA,3The redo log buffer,That is a circular buffer in the SGA that holds,information about changes made to the database.It is used to track changes made to the database by the server and background processes.,SGA,4Java pool:Used to store Java code,5Large pool:Used to store large memory structures not directly related to SQL statement processing.,2.2,Background Processes,To maximize performance and accommodate many users,a,multiprocess,Oracle system users some additional Oracle processes called background,prcesses,.,On many operating systems,background processes are created automatically when an instance is started.,1,Database Writer(DBWR):,将修改过的数据块写回到数据文件,.,The number of dirty buffers reaches a threshold value,.A process scans a specified number of blocks when scanning for free buffers and cannot find and,.Every three seconds,.A checkpoint occurs,2,Log Writer(LGWR),将,redo,日志记录写到,redo,日志文件。,.,When a transaction commits,.When the redo log buffer is one-third full,.When there is more than a megabyte of changes recorded in the redo log buffer,.Before DBW0 writes modified blocks in the database buffer cache to data files.,3,System Monitor(SMON):,执行崩溃恢复和联合自由空间。,.,Automatically recovers the instance,-Rolls forward changes in the redo logs,-Opens the database for user access,-Rolls back uncommitted transactions,.Coalesces free space,.,Deallocates,temporary segments,4,Process Monitor(PMON):,查看进程是否过早断开，释放任何容纳的锁，并处理任何其他必要的清理任务。,Cleans up after failed processes by:,.Rolling back the transaction,.Releasing locks,.Releasing other resources,5,Checkpoint Process(CKPT):,When a checkpoint occurs,Oracle must update the headers of all,datafiles,to record the details of the checkpoint.This is done by the CKPT process.The CKPT process does not write blocks to disk;,DBWn,always performs that work.,Background Processes,6,Archiver,Processes(,ARCn,):,7,Recoverer,Process(,RECn,）,8,CJQn,9,LMSn,10,Dnnn,11Server:,Snnn,12,Pnnn,:,3 小结：,Oracle server architecture:Primary Components,3.1 Memory,.Oracle Instance,1 SGA,2 Background processes,.Other processes(user/server processes),.PGA,3.2 Files,.Database files,.Other files,