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子 Latch 信息 .................................................................................................................................... 106
1.4.4.7.5 获取当前持有最热点数据块的 Latch 和 buffer 信息 ..................................................... 106
1.4.4.7.6 利用前面的 SQL 可以找到这些热点 Buffer 的对象信息 ............................................... 107
1.4.4.7.7 结合 SQL 视图可以找到操作这些对象的相关 SQL，然后通过优化 SQL 减少数据的访问，
或者优化某些容易引起争用的操作（如 connect by 等操作）来减少热点块竞争 .................... 107
1.5 等待事件 ................................................................................................................................... 108
1.5.1
等待事件的相关知识
....................................................................................................... 108
1.5.1.1 等待事件分类 ............................................................................................................................ 108
1.5.1.2 查看 v$event_name 视图的字段结构 ..................................................................................... 108
1.5.1.3 查看等待事件总数 ................................................................................................................... 108
1.5.1.4 查看等待事件分类情况 ........................................................................................................... 108
1.5.1.5 相关的几个视图 ....................................................................................................................... 109
1.5.2 33
个常见的等待事件
....................................................................................................... 110
1.5.2.1 Buffer busy waits ........................................................................................................................ 110
1.5.2.2 Buffer latch .............................................................................................................................. 111
1.5.2.3 Control file parallel write ............................................................................................................ 111
1.5.2.4 Control file sequential read ........................................................................................................ 112
1.5.2.5 Db file parallel read .................................................................................................................... 112
1.5.2.6 Db file parallel write ................................................................................................................... 112
1.5.2.7 Db file scattered read ................................................................................................................. 113
1.5.2.8 Db file sequential read ............................................................................................................... 113
1.5.2.9 Db file single write ...................................................................................................................... 113
1.5.2.10 Direct path read........................................................................................................................ 114
1.5.2.11 Direct path write ...................................................................................................................... 114
1.5.2.12 Enqueue ................................................................................................................................... 114
1.5.2.13 Free buffer waits ...................................................................................................................... 117
1.5.2.14 Latch free ................................................................................................................................. 118
1.5.2.15 Library cache lock ..................................................................................................................... 119
1.5.2.16 Library cache pin ...................................................................................................................... 119
1.5.2.17 Log file parallel write ................................................................................................................ 119
1.5.2.18 Log buffer space ....................................................................................................................... 120
1.5.2.19 Log file sequential read ............................................................................................................ 120
1.5.2.20 Log file single write .................................................................................................................. 120
1.5.2.21 Log file switch(archiving needed) ............................................................................................. 120
1.5.2.22 Log file switch(checkpoint incomplete) .................................................................................... 121
1.5.2.23 Log file sync .............................................................................................................................. 121
1.5.2.24 SQL*Net break/reset to client .................................................................................................. 122
1.5.2.25 SQL*Net break/reset to dblink ................................................................................................. 122
1.5.2.26 SQL*Net message from client .................................................................................................. 122
1.5.2.27 SQL*Net message from dblink ................................................................................................. 122
1.5.2.28 SQL*Net message to client ....................................................................................................... 123
1.5.2.29 SQL*Net message to dblink ...................................................................................................... 123
1.5.2.30 SQL*Net more data from client ................................................................................................ 123
1.5.2.31 SQL*Net more data from dblink ............................................................................................... 123
