今天在查看bdump\cdmp\orcl2_p123_54321.trw的文件内容时，发现有"PX Deq: reap credit"等待事件，于是就到mos中搜索了一下：
WAITEVENT: "PX Deq: reap credit" (文档 ID 250947.1)
该等待事件的说明如下：
This wait event indicates that we are doing a non-blocking test to see if any channel has returned a message. We should see that although there is a high number of these events, the time accumulated to it should be zero (or really low).
相关参考网址：http://www.eygle.com/archives/2009/09/px_deq_reap_credit.html
原文：http://blog.csdn.net/msdnchina/article/details/44626925