SQL> select eventTOTAL_WAITS TIME_WAITEDAVERAGE_WAIT from v$session_event where sid= order by TIME_WAITED desc;
EVENT TOTAL_WAITS
TIME_WAITED AVERAGE_WAIT
db file sequential read
free buffer waits
log file switch completion
EVENT TOTAL_WAITS
TIME_WAITED AVERAGE_WAIT
log file sync
SQL*Net message from client
latch free
EVENT TOTAL_WAITS
TIME_WAITED AVERAGE_WAIT
log file switch (checkpoint incomplete)
SQL*Net more data from client
enqueue
EVENT TOTAL_WAITS
TIME_WAITED AVERAGE_WAIT
undo segment extension
write complete waits
buffer busy waits
EVENT TOTAL_WAITS
TIME_WAITED AVERAGE_WAIT
SQL*Net message to client
file open
发现db file sequential read 居高通常在单块读发生该事件用于索引读取察看正在导入数据的表果然索引俱全导入数据的时候要维护索引对每个导入的数据都要找到对应的索引叶结点插入新索引enry 删除索引后该等待事件降低
通常如果发生较高的log file sync 事件表示导入进程提交过于频繁增加buffer参数可以减少commit次数减少该等待事件
