From :

SCOPE & APPLICATION
-------------------

This is intended as a reference for anyone involved in database tuning.

At the moment we consider the following PX wait events as idle:
- "PX Idle Wait"
- "PX Deq: Execution Msg"
- "PX Deq: Table Q Normal"
- "PX Deq Credit: send blkd"
- "PX Deq: Execute Reply"
- "PX Deq Credit: need buffer"
- "PX Deq: Signal ACK"
- "PX Deque wait"

In 9i statspack does not filter out all idle PX wait event in
the Top 5 wait event section. So it can happen that you see
a PX idle wait event in this section.

The full list of Parallel Execution wait events are documented here
for completeness.

Parallel Execution Wait Events
------------------------------

Parallel Recovery
=================
"PX Deq: Par Recov Reply"
"PX Deq: Par Recov Execute"
"PX Deq: Par Recov Change Vector"
Replication
===========
"Replication Dequeue "
"waiting for slave message"

Parallel Query
==============
"PX Deq: Table Q Normal" Note 270921.1
"PX Deq: Table Q Sample"
"PX Deq: Table Q qref"
"PX Deq: Table Q Get Keys"
"PX Deq: Table Q Close"

Index Operations
================
"PX Deq: Merge Reply"
"PX Deq: Index Merge Execute"
"PX Deq: Index Merge Close"
General Parallel Execution
==========================
"PX qref latch" Note 240145.1
"PX server shutdown" Note 250357.1
"PX create server" obsolete since Oracle 8.0
"PX signal server"
"PX Deque wait"
"PX Idle Wait" Note 257595.1
"PX Deq: Join ACK" Note 250960.1
"PX Deq Credit: need buffer" Note 253912.1
"PX Deq Credit: free buffer"
"PX Deq Credit: send blkd"
"PX Deq: Test for msg"
"PX Deq: Signal ACK" Note 257594.1
"PX Deq: reap credit" Note 250947.1
"PX Nsq: PQ descriptor query"
"PX Nsq: PQ load info query"
"PX Deq: Msg Fragment" Note 254760.1
"PX Deq: Parse Reply" Note 257596.1
"PX Deq: Execute Reply" Note 270916.1
"PX Deq: Execution Msg" Note 69067.1

Parallel Transaction Recovery
=============================
"PX Deq: Txn Recovery Start"
"PX Deq: Txn Recovery Reply" [@more@]

Parallel Query Wait Events

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