What are the following wait events? Can anyone elaborate it in details?
PX Deq: Table Q Sample
PX Deq Credit: send blkd
PX Deq: Join AC
PX Deq: Signal ACK
PX Deq: Msg Fragment
direct path read
PX qref latch
SQL> select event,total_waits,time_waited,wait_class from v$system_event order by total_waits;
EVENT TOTAL_WAITS TIME_WAITED WAIT_CLASS
------------------------------ ----------- ----------- --------------------
db file scattered read 9333287 2471813 User I/O
*PX Deq: Table Q Sample 11401065 43684227 Idle*
*PX Deq Credit: send blkd 13798394 25448649 Other*
SQL*Net message from client 20767011 1179217392 Idle
SQL*Net message to client 20767019 2618 Network
*PX Deq: Join ACK 23735308 1022426 Idle*
*PX Deq: Parse Reply 24882798 1278726 Idle*
rdbms ipc message 25223968 2147012652 Idle
*PX Deq: Signal ACK 26615286 27873560 Other*
cursor: mutex X 26745289 52071 Concurrency
*PX Deq: Msg Fragment 43670924 78219774 Idle*
EVENT TOTAL_WAITS TIME_WAITED WAIT_CLASS
------------------------------ ----------- ----------- --------------------
PX Idle Wait 68927042 4364594403 Idle
PX Deq: Execute Reply 88498025 4326377 Idle
PX Deq: Execution Msg 823922687 792964190 Idle
*direct path read 1274423531 7242769 User I/O*
*PX qref latch 2.3745E+11 49638018 Other*
122 rows selected.