几个视图的功能，来自官方文档
v$sqltext
V$SQLTEXT displays the text of SQL statements belonging to shared SQL cursors in the SGA.
V$SESSION
V$SESSION displays session information for each current session.
v$wait_chains
V$WAIT_CHAINS displays information about blocked sessions. A wait chain is comprised of sessions that are blocked by one another. Each row represents a blocked and blocker session pair. If a wait chain is not a cyclical wait chain, then the last row for the chain does not have a blocker.
找到造成等待的SQL