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.

Column	Datatype	Description
`CHAIN_ID`	`NUMBER`	A number identifying the wait chain
`CHAIN_IS_CYCLE`	`VARCHAR2(5)`	Indicates whether the final blocked session in the wait chain is blocked by the initial blocked session (`TRUE`) or not (`FALSE`)
`CHAIN_SIGNATURE`	`VARCHAR2(801)`	An Oracle-specific text signature of the wait chain. This signature can be used to identify similar wait chains.
`CHAIN_SIGNATURE_HASH`	`NUMBER`	A numeric representation of `CHAIN_SIGNATURE`
`INSTANCE`	`NUMBER`	Blocked session's instance identifier
`OSID`	`VARCHAR2(25)`	Blocked session's operating system process identifier
`PID`	`NUMBER`	Blocked session's Oracle process identifier
`SID`	`NUMBER`	Blocked session's Oracle session identifier
`SESS_SERIAL#`	`NUMBER`	Blocked session's Oracle session serial number
`BLOCKER_IS_VALID`	`VARCHAR2(5)`	Indicates whether the blocked session has a blocker (`TRUE`) or not (`FALSE`)
`BLOCKER_INSTANCE`	`NUMBER`	Blocker session's instance identifier; NULL if `BLOCKER_IS_VALID` is `FALSE`
`BLOCKER_OSID`	`VARCHAR2(25)`	Blocker session's operating system process identifier; NULL if `BLOCKER_IS_VALID` is `FALSE`
`BLOCKER_PID`	`NUMBER`	Blocker session's Oracle process identifier; NULL if `BLOCKER_IS_VALID` is `FALSE`
`BLOCKER_SID`	`NUMBER`	Blocker session's Oracle session identifier; NULL if `BLOCKER_IS_VALID` is `FALSE`
`BLOCKER_SESS_SERIAL#`	`NUMBER`	Blocker session's Oracle session serial number; NULL if `BLOCKER_IS_VALID` is `FALSE`
`BLOCKER_CHAIN_ID`	`NUMBER`	If not NULL, then the blocker session is a member of another chain specified by this chain identifier. For the remaining wait chain information, see the wait chain with the specified `CHAIN_ID`.
`IN_WAIT`	`VARCHAR2(5)`	Indicates whether the blocked session is in a wait (`TRUE`) or not (`FALSE`)
`TIME_SINCE_LAST_WAIT_SECS`	`NUMBER`	Number of seconds since the last time the blocked session waited; NULL if `IN_WAIT` is `TRUE`
`WAIT_ID`	`NUMBER`	A number identifying the wait; NULL if `IN_WAIT` is `FALSE`
`WAIT_EVENT`	`NUMBER`	Resource or event number for which the blocked session is waiting; NULL if `IN_WAIT` is `FALSE`
`WAIT_EVENT_TEXT`	`VARCHAR2(64)`	Resource or event for which the blocked session is waiting; NULL if `IN_WAIT` is `FALSE`
`P1`	`NUMBER`	First additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`P1_TEXT`	`VARCHAR2(64)`	Description of the first additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`P2`	`NUMBER`	Second additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`P2_TEXT`	`VARCHAR2(64)`	Description of the second additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`P3`	`NUMBER`	Third additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`P3_TEXT`	`VARCHAR2(64)`	Description of the third additional wait parameter; NULL if `IN_WAIT` is `FALSE`
`IN_WAIT_SECS`	`NUMBER`	Seconds the blocked session has been in the current wait; NULL if `IN_WAIT` is `FALSE`
`TIME_REMAINING_SECS`	`NUMBER`	Seconds remaining until the blocked session ends its wait (`-1` if the blocked session can indefinitely wait); NULL if `IN_WAIT` is `FALSE`
`NUM_WAITERS`	`NUMBER`	Number of sessions waiting for the blocked session
`ROW_WAIT_OBJ#`	`NUMBER`	Object ID for the table containing the row specified in `ROW_WAIT_ROW#`; NULL if `IN_WAIT` is `FALSE`
`ROW_WAIT_FILE#`	`NUMBER`	Identifier for the datafile containing the row specified in `ROW_WAIT_ROW#`; NULL if `IN_WAIT` is `FALSE`. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of `ROW_WAIT_OBJ#` is not `-1`.
`ROW_WAIT_BLOCK#`	`NUMBER`	Identifier for the block containing the row specified in `ROW_WAIT_ROW#`; NULL if `IN_WAIT` is `FALSE`. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of `ROW_WAIT_OBJ#` is not `-1`.
`ROW_WAIT_ROW#`	`NUMBER`	Current row being locked; NULL if `IN_WAIT` is `FALSE`. This column is valid only if the blocked session is currently waiting for another transaction to commit and the value of `ROW_WAIT_OBJ#` is not `-1`.