Configuring Extract for ALO mode

To configure Extract for ALO mode, follow these steps as part of the overall process for configuring Oracle GoldenGate.

Enable supplemental logging at the table level and the database level for the tables in the source database. (See Configuring Logging Properties .)
When Oracle GoldenGate is running on a different server from the source database, make certain that SQL*Net is configured properly to connect to a remote server, such as providing the correct entries in a TNSNAMES file. Extract must have permission to maintain a SQL*Net connection to the source database.
Use a SQL*Net connect string for the name of the user in the credential store that is assigned to the process. Specify the alias of this user in the following:
- The USERIDALIAS parameter in the parameter file of every Oracle GoldenGate process that connects to that database.
- The USERIDALIAS portion of the DBLOGIN command in GGSCI.
Note:

If you have a standby server that is local to the server that Oracle GoldenGate is running on, you do not need to use a connect string for the user specified in USERIDALIAS. You can just supply the user login name.

See Creating and Populating the Credential Store in Oracle GoldenGate Security Guide for more information about using a credential store.
Use the Extract parameter TRANLOGOPTIONS with the ARCHIVEDLOGONLY option. This option forces Extract to operate in ALO mode against a primary or logical standby database, as determined by a value of PRIMARY or LOGICAL STANDBY in the db_role column of the v$database view. The default is to read the online logs. TRANLOGOPTIONS with ARCHIVEDLOGONLY is not needed if using ALO mode against a physical standby database, as determined by a value of PHYSICAL STANDBY in the db_role column of v$database. Extract automatically operates in ALO mode if it detects that the database is a physical standby.
Other TRANLOGOPTIONS options might be required for your environment. For example, depending on the copy program that you use, you might need to use the COMPLETEARCHIVEDLOGONLY option to prevent Extract errors.
Use the MAP parameter for Extract to map the table names to the source object IDs..
Add the Extract group by issuing the ADD EXTRACT command with a timestamp as the BEGIN option, or by using ADD EXTRACT with the SEQNO and RBA options. It is best to give Extract a known start point at which to begin extracting data, rather than by using the NOW argument. The start time of NOW corresponds to the time of the current online redo log, but an ALO Extract cannot read the online logs, so it must wait for that log to be archived when Oracle switches logs. The timing of the switch depends on the size of the redo logs and the volume of database activity, so there might be a lag between when you start Extract and when data starts being captured. This can happen in both regular and RAC database configurations.