DBA_LOGSTDBY_HISTORY

DBA_LOGSTDBY_HISTORY displays the history of switchovers and failovers in a Data Guard configuration. It does this by showing the complete sequence of redo log streams processed or created on the local system, across all role transitions. (After a role transition, a new log stream is started and the log stream sequence number is incremented by the new primary database.) This view is for logical standby databases only.

Column Datatype NULL Description
STREAM_SEQUENCE# NUMBER   Lists the sequence numbers for all log streams created or applied on the local system.

Note: A value of 0 indicates an unknown sequence order; this is reserved for future log streams.
STATUS VARCHAR2(16)   Description of the log stream processing:

  • Past - The log stream has already been processed

  • Immediate Past - This is the most recently processed log stream; its status is transitioning from Current to Past

  • Current - The log stream is currently being processed

  • Immediate Future - This is the next log stream to be processed; its status is transitioning from Future to Current

  • Future - The log stream will be processed
SOURCE VARCHAR2(5)   Describes how the log stream was started:

  • RFS - The RFS process created the log stream

  • User - A user registered the initial log file for the log stream

  • Synch - A user issued the ALTER DATABASE START LOGICAL STANDBY APPLY NEW PRIMARY DDL statement

  • Redo - The log stream information was recorded in the redo log
DBID NUMBER   Database identifier of the primary database that created the log stream
FIRST_CHANGE# NUMBER   Lowest system change number (SCN) in the current log file
LAST_CHANGE# NUMBER   Highest system change number (SCN) in the current log file
FIRST_TIME DATE   Time of the first SCN entry (FIRST_CHANGE#) in the current log file
LAST_TIME DATE   Time of the last SCN entry (LAST_CHANGE#) in the current log file
DGNAME VARCHAR2(255)   Unique database name (DB_UNIQUE_NAME) of the primary database that produced the log stream. See V$DATAGUARD_CONFIG to display all database DB_UNIQUE_NAME values defined in the Data Guard configuration.
MERGE_CHANGE# NUMBER   SCN that should be used to flashback a failed primary (that created the log stream) or to flashback a bystander logical standby database following a failover, in the context of the associated redo log stream. It is the SCN up to which redo for the associated log stream can be merged safely in all databases using local copies of archived logs received from the primary database. In order to apply changes beyond this following a failover, you will need to fetch and mine the redo logs from the failover target.
PROCESSED_CHANGE# NUMBER   Strict upper bound on the SCN up to which SQL Apply has applied redo records before it switched to a new log stream (either because it was activated and became the primary database, or in the case of a bystander logical standby database where it switched to a new log stream in order to accommodate a new primary database).