<p style="padding-top: 6px; padding-bottom: 6px; margin-top: 0px; margin-bottom: 0px; color: rgb(51, 51, 51); font-family: 'Trebuchet MS', Tahoma, Arial; line-height: 18px; "><pre name="code" class="sql">直接路径写（direct paht write）通常发生在Oracle直接从PGA写数据到数据文件或临时文件，这个写操作可以绕过SGA。直接路径写等待事件的3个参数分别是：file number（指绝对文件号）、first dba和block cnt数量，在Oracle 10g/11g中，这个等待事件同direct path read一样被归于User I/O一类。
这类写入操作通常在以下情况被使用：
·直接路径加载；
·并行DML操作；
·磁盘排序；
·对未缓存的“LOB”段的写入，随后会记录为direct path write(lob)等待。
SQL> select * from v$mystat where rownum<2;
SID STATISTIC# VALUE
---------- ---------- ----------
192 0 0
SQL> create table test1 as select * from F_AGT_GCI_BUSINESS_INFO_H;
SQL> select sid,event,p1,p2,p3 from v$session_wait where sid=192;
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 14 1746176 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 8 3446368 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 9 1760896 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 7 1795968 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 21 3394464 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 21 1769984 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 20 1772672 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 16 3360288 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 14 3328384 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 13 3316992 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 12 3317696 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 13 1729032 120
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 12 1734784 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 11 1745152 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 7 3467584 32
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path read 10 1751296 128
SQL> /
SID EVENT P1 P2 P3
---------- ---------------------------------------------------------------- ---------- ---------- ----------
192 direct path write 5 3406944 32
direct path write 稳定在32左右
direct path read/write 都是通过server process读写的吧