# Working with the EXTRACT and REPLICAT utilities of Oracle GoldenGate
<a name="Appendix.OracleGoldenGate.ExtractReplicat"></a>

The Oracle GoldenGate utilities `EXTRACT` and `REPLICAT` work together to keep the source and target databases in sync via incremental transaction replication using trail files. All changes that occur on the source database are automatically detected by `EXTRACT`, then formatted and transferred to trail files on the Oracle GoldenGate on-premises or Amazon EC2 instance hub. After initial load is completed, the data is read from these files and replicated to the target database by the `REPLICAT` utility.

## Running the Oracle GoldenGate EXTRACT utility
<a name="Appendix.OracleGoldenGate.Extract"></a>

The `EXTRACT` utility retrieves, converts, and outputs data from the source database to trail files. The basic process is as follows:

1. `EXTRACT` queues transaction details to memory or to temporary disk storage.

1. The source database commits the transaction.

1. `EXTRACT` writes the transaction details to a trail file.

1. The trail file routes these details to the Oracle GoldenGate on-premises or the Amazon EC2 instance hub and then to the target database.

The following steps start the `EXTRACT` utility, capture the data from `EXAMPLE.TABLE` in source database `OGGSOURCE`, and create the trail files. 

**To run the EXTRACT utility**

1. Configure the `EXTRACT` parameter file on the Oracle GoldenGate hub (on-premises or Amazon EC2 instance). The following listing shows an example `EXTRACT` parameter file named `$GGHOME/dirprm/eabc.prm`.

   ```
   EXTRACT EABC
    
   USERID oggadm1@OGGSOURCE, PASSWORD "my-password"
   EXTTRAIL /path/to/goldengate/dirdat/ab 
    
   IGNOREREPLICATES
   GETAPPLOPS
   TRANLOGOPTIONS EXCLUDEUSER OGGADM1
   	 
   TABLE EXAMPLE.TABLE;
   ```

1. On the Oracle GoldenGate hub, log in to the source database and launch the Oracle GoldenGate command line interface `ggsci`. The following example shows the format for logging in.

   ```
   dblogin oggadm1@OGGSOURCE
   ```

1. Add transaction data to turn on supplemental logging for the database table.

   ```
   add trandata EXAMPLE.TABLE
   ```

1. Using the `ggsci` command line, enable the `EXTRACT` utility using the following commands.

   ```
   add extract EABC tranlog, INTEGRATED tranlog, begin now
   add exttrail /path/to/goldengate/dirdat/ab 
      extract EABC, 
      MEGABYTES 100
   ```

1. Register the `EXTRACT` utility with the database so that the archive logs are not deleted. This task allows you to recover old, uncommitted transactions if necessary. To register the `EXTRACT` utility with the database, use the following command.

   ```
   register EXTRACT EABC, DATABASE
   ```

1. Start the `EXTRACT` utility with the following command.

   ```
   start EABC
   ```

## Running the Oracle GoldenGate REPLICAT utility
<a name="Appendix.OracleGoldenGate.Replicat"></a>

The `REPLICAT` utility "pushes" transaction information in the trail files to the target database.

The following steps enable and start the `REPLICAT` utility so that it can replicate the captured data to the table `EXAMPLE.TABLE` in target database `OGGTARGET`.

**To run the REPLICATE utility**

1. Configure the `REPLICAT` parameter file on the Oracle GoldenGate hub (on-premises or EC2 instance). The following listing shows an example `REPLICAT` parameter file named `$GGHOME/dirprm/rabc.prm`.

   ```
   REPLICAT RABC
    
   USERID oggadm1@OGGTARGET, password "my-password"
    
   ASSUMETARGETDEFS
   MAP EXAMPLE.TABLE, TARGET EXAMPLE.TABLE;
   ```
**Note**  
Specify a password other than the prompt shown here as a security best practice.

1. Log in to the target database and launch the Oracle GoldenGate command line interface (`ggsci`). The following example shows the format for logging in.

   ```
   dblogin userid oggadm1@OGGTARGET
   ```

1. Using the `ggsci` command line, add a checkpoint table. The user indicated should be the Oracle GoldenGate user account, not the target table schema owner. The following example creates a checkpoint table named `gg_checkpoint`.

   ```
   add checkpointtable oggadm1.oggchkpt
   ```

1. To enable the `REPLICAT` utility, use the following command.

   ```
   add replicat RABC EXTTRAIL /path/to/goldengate/dirdat/ab CHECKPOINTTABLE oggadm1.oggchkpt 
   ```

1. Start the `REPLICAT` utility by using the following command.

   ```
   start RABC
   ```