ne more thing to add. We have just finished our own battle with this same wait
RE: Tx - row lock contention after implementing transaction management in application server - oracle-l - FreeLists
event. In our case, it resulted from 2 sessions inserting same value into a UK
constraint. This scenario will also post the very same event. We disabled the
constraint and the event totally disappeared from sql perf profile.
Primary Key に同じ値を insert すると、トランザクション・ロック(TX)の競合が発生する - ablog
に書いたのと同じやつだ。結構よくあるのかな。