1 Oracle启动选项;
Oracle数据库在startup启动时，Oracle将在默认位置$ORACLE_HOME/dbs中查找初始化参数文件；Oracle以下面的顺序在其中寻找合适的初始化文件：
Spfile$ORACLE_SID.ora
Spfile.ora
Init$ORACLE_SID.ora
可以用几种方式启动oracle数据库，不同方式启动将影响启动数据库的程度，启动状态由nomount(数据库未装载)——>mount(数据库完成装载)——>open(数据库打开)
1.1 STARTUP NOMOUNT;
sql>startupnomount ORACLEinstancestarted. TotalSystemGlobalArea1603411968bytes FixedSize 2253664bytes VariableSize 1375734944bytes DatabaseBuffers 218103808bytes RedoBuffers 7319552bytes
Oracle读参数文件，打开实例，启动Oracle后台进程,给Oracle分配SGA。此时数据库状态为未装载。
1.2 ALTER DATABASE MOUNT;
sql>alterdatabasemount; Databasealtered.
Oracle 打开并读取控制文件，获取数据文件和重做日志文件的名称和位置。此时数据库完成装载。
1.3 ALTER DATABASE OPEN;
sql>alterdatabaSEOpen; Databasealtered.
Oracle打开数据文件和重做日志文件，至此Oracle可以对外提供服务。
2 通过10046事件查看内部启动过程
sql>startupnomount; TotalSystemGlobalArea1603411968bytes FixedSize 2253664bytes VariableSize 1375734944bytes DatabaseBuffers 218103808bytes RedoBuffers 7319552bytes sql>oradebugsetmypid Statementprocessed. sql>oradebugtracefile_name /oracle/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_3682.trc sql>altersessionsetevents'10046tracenamecontextforever,level12'; Sessionaltered. sql>alterdatabasemount; Databasealtered. sql>alterdatabaSEOpen; Databasealtered.
查看udump文件
[oracle@rhel6~]$more/oracle/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_3682.trc
Tracefile/oracle/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_3682.trc OracleDatabase11gEnterpriseEditionRelease11.2.0.4.0-64bitProduction WiththePartitioning,OLAP,DataMiningandRealApplicationTestingoptions ORACLE_HOME=/oracle/app/oracle/product/11.2.0 Systemname:Linux Nodename:rhel6 Release:2.6.32-431.el6.x86_64 Version:#1SMPSunNov1022:19:54EST2013 Machine:x86_64 VMname:VMWareVersion:6 Instancename:orcl
... WAIT#140528657591192:nam='controlfilesequentialread'ela=8file#=0block#=1blocks =1obj#=-1tim=1502627703012561 WAIT#140528657591192:nam='controlfilesequentialread'ela=2file#=1block#=1blocks =1obj#=-1tim=1502627703012583 WAIT#140528657591192:nam='controlfilesequentialread'ela=47file#=0block#=3block s=8obj#=-1tim=1502627703012650 WAIT#140528657591192:nam='controlfilesequentialread'ela=13file#=1block#=3block s=8obj#=-1tim=1502627703012674 ... WAIT#140528657591192:nam='ADRblockfileread'ela=847=0=0=0obj#=-1tim=150262 7707123048 WAIT#140528657591192:nam='ADRblockfileread'ela=576=0=0=0obj#=-1tim=150262 7707124068 WAIT#140528657591192:nam='ADRblockfileread'ela=562=0=0=0obj#=-1tim=150262 7707125013 WAIT#140528657591192:nam='ADRblockfileread'ela=473=0=0=0obj#=-1tim=150262 7707125891 ...
Oracle数据库open过程读取控制文件信息，与读取磁盘数据文件头部进行对比
alterdatabaSEOpen ENDOFSTMT PARSE#140528657591192:c=0,e=274,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=0,tim=1502627713 479605 WAIT#140528657591192:nam='controlfilesequentialread'ela=8file#=0block#=1blocks =1obj#=-1tim=1502627713479904 WAIT#140528657591192:nam='controlfilesequentialread'ela=4file#=1block#=1blocks =1obj#=-1tim=1502627713479922 WAIT#140528657591192:nam='controlfilesequentialread'ela=2file#=0block#=15block s=1obj#=-1tim=1502627713479931 ... WAIT#140528657591192:nam='DiskfileoperationsI/O'ela=11FileOperation=2fileno=1f iletype=2obj#=-1tim=1502627713481300 WAIT#140528657591192:nam='DiskfileoperationsI/O'ela=6FileOperation=2fileno=2fi letype=2obj#=-1tim=1502627713481317 WAIT#140528657591192:nam='DiskfileoperationsI/O'ela=4FileOperation=2fileno=3fi letype=2obj#=-1tim=1502627713481327 WAIT#140528657591192:nam='DiskfileoperationsI/O'ela=4FileOperation=2fileno=4fi letype=2obj#=-1tim=1502627713481338 WAIT#140528657591192:nam='DiskfileoperationsI/O'ela=5FileOperation=2fileno=201 filetype=2obj#=-1tim=1502627713481351
