7.1 Prerequisites for Configuring Replicat
This topic provides the best practices for configuring Replicat.
The guidelines to follow before configuring Replicat are:
Create the Oracle GoldenGate instance on the target system by configuring the Manager process.
See How to Add a Replicat in Using the Oracle GoldenGate Microservices Architecture.
To switch an active Replicat configuration from one mode to the other, perform these configuration steps and then see Administering Oracle GoldenGate.
7.2 What to Expect from these Instructions
These instructions show you how to configure a basic Replicat parameter (configuration) file.
Your business requirements probably will require a more complex topology, but this procedure forms a basis for the rest of your configuration steps.
By performing these steps, you can:
get the basic configuration file established.
build upon it later by adding more parameters as you make decisions about features or requirements that apply to your environment.
use copies of it to make the creation of additional Replicat parameter files faster than starting from scratch.
These instructions do not configure Replicat to apply DDL to the target. To support DDL, create the basic Replicat parameter file and then see Configuring DDL Support for configuration instructions.
7.3 Creating a Checkpoint Table
The checkpoint table is a required component of Replicat.
A Replicat maintains its recovery checkpoints in the checkpoint table, which is stored in the target database. Checkpoints are written to the checkpoint table within the Replicat transaction. Because a checkpoint either succeeds or fails with the transaction, Replicat ensures that a transaction is only applied once, even if there is a failure of the process or the database. See Before Creating Replicat in the Using the Oracle GoldenGate Microservices Architecture to learn to create checkpoint tables from the Microservices web UI.
This procedure installs a default checkpoint table, which is sufficient in most
cases. More than one checkpoint table can be used, such as to use a different
one for each Replicat group. To use a non-default checkpoint table, which
overrides the default table, use the
CHECKPOINTTABLE option of
ADD REPLICAT when you create Replicat processes in the
steps in Instantiating Oracle GoldenGate Replication. .
7.3.1 Adding the Checkpoint Table to the Target Database
- From the Oracle GoldenGate directory on the target, run GGSCI and issue the
DBLOGINcommand to log into the target database.
aliasspecifies the alias of the database login credential of a user that can create tables in a schema that is accessible to Replicat. This credential must exist in the Oracle GoldenGate credential store. For more information, see Establishing Oracle GoldenGate Credentials.
- In GGSCI, create the checkpoint table in a schema of your choice (ideally dedicated to Oracle GoldenGate).
containeris the name of the container if
schema.tableis in a multitenant container database. This container can be the root container or a pluggable database that contains the table.
schema.tableare the schema and name of the table. See Administering Oracle GoldenGate for instructions for specifying object names.
7.3.2 Specifying the Checkpoint Table in the Oracle GoldenGate Configuration
To specify the checkpoint table in the Oracle GoldenGate configuration:
- Create a
GLOBALSfile (or edit the existing one).
EDIT PARAMS ./GLOBALS
EDIT PARAMScreates a simple text file. When you save the file after
EDIT PARAMS, it is saved with the name
GLOBALSin upper case, without a file extension. It must remain as such, and the file must remain in the root Oracle GoldenGate directory.
- In the
GLOBALSfile, enter the
- Save and close the
7.3.3 Disabling Default Asynchronous COMMIT to Checkpoint Table
When a nonintegrated Replicat uses a checkpoint table, it uses an asynchronous
COMMIT with the
NOWAIT option to improve performance. Replicat can continue processing immediately after applying this
COMMIT, while the database logs the transaction in the background. You can disable the asynchronous
NOWAIT by using the
DBOPTIONS parameter with the
DISABLECOMMITNOWAIT option in the Replicat parameter file.
When the configuration of a nonintegrated Replicat group does not include a checkpoint table, the checkpoints are maintained in a file on disk. In this case, Replicat uses
WAIT to prevent inconsistencies in the event of a database failure that causes the state of the transaction, as in the checkpoint file, to be different than its state after the recovery.
7.4 Configuring Replicat
Configure a Replicat process to configure Replicat against a pluggable database. Replicat can operate in any mode within a pluggable database.
These steps configure the Replicat process.
- In GGSCI on the target system, create the Replicat parameter file.
Where: name is the name of the Replicat group.
- Enter the Replicat parameters in the order shown, starting a new line for each
parameter statement. See Table 7-* for descriptions.
Basic parameters for the Replicat group in nonintegrated mode:
REPLICAT financer USERIDALIAS tiger2 ASSUMETARGETDEFS MAP hr.*, TARGET hr2.*;
Basic parameters for the Replicat group in integrated Replicat mode:
REPLICAT financer DBOPTIONS INTEGRATEDPARAMS(parallelism 6) USERIDALIAS tiger2 ASSUMETARGETDEFS MAP hr.*, TARGET hr2.*;
groupis the name of the Replicat group.
Applies to Replicat in nonintegrated mode.
DEFERREFCONSTsets constraints to
DEFERRABLEto delay the enforcement of cascade constraints by the target database until the Replicat transaction is committed. See Reference for Oracle GoldenGate for additional important information.
DBOPTIONS INTEGRATEDPARAMS (
This parameter specification applies to Replicat in integrated mode. It specifies optional parameters for the inbound server.
See Optional Parameters for Integrated Modesfor additional important information about these
Specifies the alias of the database login credential of the user that is assigned to Replicat. This credential must exist in the Oracle GoldenGate credential store. For more information, see Establishing Oracle GoldenGate Credentials
Specifies the relationship between a source table or sequence, or multiple objects, and the corresponding target object or objects.
MAPspecifies the source table or sequence, or a wildcarded set of objects.
TARGETspecifies the target table or sequence or a wildcarded set of objects.
containeris the name of a container, if the source database is a multitenant container database.
schemais the schema name or a wildcarded set of schemas.
objectis the name of a table or sequence, or a wildcarded set of objects.
Terminate this parameter statement with a semi-colon.
To exclude objects from a wildcard specification, use the
For more information and for additional options that control data filtering, mapping, and manipulation, see
MAPin Reference for Oracle GoldenGate.
- If using integrated Replicat or parallel Replicat in integrated mode, add the
following parameters to the Extract parameter file:
LOGALLSUPCOLS: This parameter ensures the capture of the supplementally logged columns in the before image. It's the default parameter and shouldn't be turned off or disabled. It is valid for any source database that is supported by Oracle GoldenGate. For Extract versions older than 12c, you can use
NOCOMPRESSDELETESparameters to satisfy the same requirement. The database must be configured to log the before and after values of the primary key, unique indexes, and foreign keys.
UPDATERECORDFORMATparameter set to COMPACT: This setting causes Extract to combine the before and after images of an
UPDATEoperation into a single record in the trail. This is the default option and it is recommended that you don't change the default setting.
- Enter any optional Replicat parameters that are recommended for your configuration. You can edit this file at any point before starting processing by using the
EDIT PARAMScommand in GGSCI. For more information, see the Reference for Oracle GoldenGate and Optional Parameters for Integrated Modes for additional configuration considerations..
- Save and close the file.
See Administering Oracle GoldenGate for important information about making configuration changes to Replicat once processing is started, if using integrated Replicat.
7.5 Next Steps
Once you have created a basic parameter file for Replicat, see the following for additional configuration steps.
Additional Configuration Steps For Using Nonintegrated Replicat (if using nonintegrated Replicat)
Configuring DDL Support (to use Oracle GoldenGate DDL support)