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Oracle® Database Reference
11g Release 1 (11.1)

Part Number B28320-01
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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.