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在一次周末的课程试验中，频繁的看到 Data file init write 等待事件。

在这里做一点记录说明，以下是来自跟踪文件的记录信息：

以下是引用片段：

WAIT #2: nam='Data file init write' ela= 13031 count=1 intr=256 timeout=-1 obj#=51706

tim=6068271611

WAIT #2: nam='Data file init write' ela= 118163 count=1 intr=256 timeout=-1

obj#=51706 tim=6068392491

WAIT #2: nam='Data file init write' ela= 94036 count=1 intr=256 timeout=-1

obj#=51706 tim=6068490286

WAIT #2: nam='Data file init write' ela= 52412 count=1 intr=256 timeout=-1

obj#=51706 tim=6068545333

WAIT #2: nam='Data file init write' ela= 4 count=0 intr=32 timeout=2147483647

obj#=51706 tim=6068545596

WAIT #2: nam='Data file init write' ela= 26 count=1 intr=32 timeout=2147483647

obj#=51706 tim=6068545641

WAIT #2: nam='Data file init write' ela= 101743 count=1 intr=256 timeout=-1

obj#=51706 tim=6068648487

WAIT #2: nam='Data file init write' ela= 44854 count=1 intr=256 timeout=-1

obj#=51706 tim=6068694281

WAIT #2: nam='Data file init write' ela= 52841 count=1 intr=256 timeout=-1

obj#=51706 tim=6068748054

WAIT #2: nam='Data file init write' ela= 48984 count=1 intr=256 timeout=-1

obj#=51706 tim=6068798310

WAIT #2: nam='Data file init write' ela= 3 count=0 intr=32 timeout=2147483647

obj#=51706 tim=6068798365

WAIT #2: nam='Data file init write' ela= 26 count=1 intr=32 timeout=2147483647

obj#=51706 tim=6068798409

WAIT #2: nam='Data file init write' ela= 101899 count=1 intr=256 timeout=-1

obj#=51706 tim=6068900931

WAIT #2: nam='Data file init write' ela= 21 count=-1 intr=32 timeout=2147483647

obj#=51706 tim=6068901053

测试数据库是Oracle10g 10.2.0.3，实际上这个等待事件也是从Oracle 10g开始引入的，用来标识表空间或数据文件扩展时的等待。

Oracle 需要将系统块格式化为Oracle数据块，然后才能提供数据库使用。

在这个流程处理中，Oracle经过如下三个步骤：

1、扩展数据文件

select file# from file$ where ts#=:1

2、更新用户空间限额

update tsq$ set blocks=:3,maxblocks=:4,grantor#=:5,priv1=:6,priv2=:7,priv3=:8 where ts#=:1 and user#=:2

3、扩展数据段

update seg$ set type#=:4,blocks=:5,extents=:6,minexts=:7,maxexts=:8,extsize=:9,extpct=:10,user#=:11,iniexts=:12,lists=decode(:13, 65535, NULL, :13),groups=decode(:14, 65535, NULL, :14), cachehint=:15, hwmincr=:16, spare1=DECODE(:17,0,NULL,:17),scanhint=:18 where ts#=:1 and file#=:2 and block#=:3

这就是Oracle10g中空间扩展时内部流程。

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