Oracle Wait Event:Data file init write
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。
