The Replication Agent for Oracle must be
installed on a machine where it can directly access the Oracle redo
log and archive log files.
You can access both online and archive logs by default. If you want to access only the online logs, the Replication Agent can be configured to do so, but it requires that you turn auto-archiving off and requires Replication Agent to issue manual archive log commands to Oracle.
When the default is used and archive log files are to be accessed, the Replication Agent must be configured to use the directory path where the archive log files are located. To prevent conflicts with other archive file processes, you may wish to configure Oracle to produce archive log files into an additional directory used only for replication. Replication Agent can be configured to remove archive log files when they are no longer needed. Sybase recommends that you configure the Replication Agent to remove archive log files only if an additional directory is used.
This section discusses access to Oracle archived redo
logs that are stored as file-system files. If the archived redo
logs are stored using the Oracle ASM, see “Automatic Storage Management” for details.
Replication Agent for Oracle requires the following settings in your Oracle database:
Redo log archiving must be enabled:
alter database ARCHIVELOG;
If you are using Oracle Real Application Clusters (RAC),
you must enable redo log archiving for each instance in the cluster.
Verify that log archiving is enabled:
select log_mode from v$database;
If you are using Oracle RAC, use the following SQL to verify that log archiving has been enabled:
select instance, name, log_mode from gv$database;
Automatic redo log archiving must be disabled.
If ARCHIVELOG (ARCHIVELOG or MANUAL in Oracle 10g) is returned, then log archiving is enabled.
When pdb_include_archives is set to true, the default, the Replication Agent does not do archiving and Sybase recommends that you configure Oracle to do automatic archiving of redo logs.
When the configuration parameter pdb_include_archives is set to false, Replication Agent for Oracle requires that automatic archiving of Oracle redo logs be disabled. Archiving is performed manually by the Replication Agent as the data in the redo log files is replicated.
Replication Agent for Oracle requires the following settings in your Oracle database depending on the Oracle version.
To disable automatic archiving
Make sure you have SYSDBA administrator privileges, and close the database.
Enter the following:
alter database ARCHIVELOG MANUAL;
To verify that log archiving is disabled:
select log_mode from v$database;
If MANUAL is returned, then automatic log archiving is disabled.
To disable automatic archiving
To change the LOG_ARCHIVE_START parameter, you can manually edit the server’s start-up parameter file or use the following Oracle command:
alter system set log_archive_start=false scope=spfile;
To check the setting of the LOG_ARCHIVE_START parameter:
select value from v$system_parameter where name = 'log_archive_start';
If false is returned, the value in the server parameter file has been correctly modified to prevent automatic archiving when you re-start the Oracle server. For more information about the LOG_ARCHIVE_START parameter or the ALTER SYSTEM commands, see the Oracle Database Reference Guide.
Automatic archiving must be disabled in the active server and when you re-start the Oracle server. To stop automatic archiving in the active server:
alter system archive log stop;
To disable automatic archiving when you re-start the Oracle server, change the value of the server’s LOG_ARCHIVE_START parameter to false.
This note applies only when pdb_include _archives is
set to false. For redo log file processing after
Replication Agent for Oracle is initialized, automatic archiving
must never be enabled, even temporarily. If
automatic archiving is re-enabled or manual archiving is performed,
causing a redo log file not yet processed by the Replication Agent
to be overwritten, then the data in the lost redo log file will
not be replicated. You CAN recover from this situation by reconfiguring
the Replication Agent to access archive log files. Set pdb_include_archives to true,
set pdb_archive_path to the
directory location that contains the archive of the file that has
been overwritten, and resume. After catching up, suspend the Replication Agent,
and reset pdb_include_archives to false.
You can enable the forced logging of all database changes to the Oracle redo log file. Sybase recommends setting this option to insure that all data that should be replicated is logged. To enable the force logging command, execute the following statement on the primary database:
alter database FORCE LOGGING;
To verify the current setting of the force logging command, execute the following statement on the primary database:
select force_logging from v$database;
