START EXTRACT to start the Extract process. To confirm that Extract has started, use the
INFO EXTRACT or
STATUS EXTRACT command. Extract can be started at its normal start point (from initial or current checkpoints) or from an alternate, user-specified position in the data source.
START EXTRACT directs a primary Extract and a data pump Extract to start processing at one of the following locations in the data source to maintain data integrity:
After graceful or abnormal termination: At the first unprocessed transaction in the data source from the previous run, as represented by the current read checkpoint.
First-time startup after the group was created: At the start point specified with the
ADD EXTRACT command.
See Administering Oracle GoldenGate for Windows and UNIX for more information about checkpoints.
Extract also can be started from the command line of the operating system for certain synchronization configurations. For more information on the proper configuration and startup method to use for your purposes, see Administering Oracle GoldenGate for Windows and UNIX.
AFTERCSN options enable you to establish a logical starting point for a primary Extract or a data pump, after you establish an approximate physical starting point with the
ADD EXTRACT or
ALTER EXTRACT command. For example, in an initial-load scenario, after a backup is applied to the target, the serial identifier of the last transaction (such as an Oracle SCN) can be mapped to an Oracle GoldenGate CSN (commit sequence number) value, which can be used to start Extract with the
AFTERCSN option. By starting with the first transaction after the specified CSN, Extract omits the transactions that were included in the backup, which would otherwise cause duplicate-record and missing-record errors.
Before starting Extract with
AFTERCSN, you must establish a physical starting location with one of the following commands:
ADD EXTRACT with the
BEGIN option set to a timestamp that is earlier than the CSN value specified with
AFTERCSN. The transaction log that contains the timestamp and every log thereafter must be available on the system before Extract is started.
ALTER EXTRACT to the sequence number of the log that contains the CSN specified with
Note:See Administering Oracle GoldenGate for Windows and UNIX for more information about the values that comprise a CSN for a given database.
START EXTRACT group_name [ATCSN csn | AFTERCSN csn]
The name of an Extract group or a wildcard (*) to specify multiple groups. For example, T* starts all Extract groups whose names begin with T.
Specifies an alternate start point. (See "Alternate Start Point" for usage instructions.)
Directs Extract to position its start point at the first transaction that has the specified CSN. Any transactions in the data source that have CSN values less than the specified one are skipped.
Directs Extract to position its start point at the beginning of the first transaction after the one that has the specified CSN. Any transactions in the data source that have CSN values that are less than, or equal to, the specified one are skipped.
Specifies a CSN value. Enter the CSN value in the format that is valid for the database. See Administering Oracle GoldenGate for Windows and UNIX for CSN formats and descriptions. Extract abends if the format is invalid and writes a message to the report file. To determine the CSN to supply after an initial load is complete, use the serial identifier at which the load utility completed. Otherwise, follow the instructions in the initial load procedure for determining when to start Extract.
The following are additional guidelines to observe when using
To support starting at, or after, a CSN, the trail must be of Oracle GoldenGate version 10.0.0 or later, because the CSN is stored in the file header so that it is available to downstream processes.
When a record that is specified with a CSN is found, Extract issues a checkpoint. The checkpoint ensures that subsequent Extract startups begin from the requested location, and not from a point prior to the requested CSN.
You must establish a physical start point in the transaction log or trail for Extract with
ADD EXTRACT or
ALTER EXTRACT before using
AFTERCSN. These options are intended to be an additional filter after Extract is positioned to a physical location in the data source.