GoldenGate on Exadata

Oracle Exadata Database Machine has already been mentioned in this chapter. The Oracle engineered solution, depending on its configuration, features a number of Oracle database servers configured for RAC, offering high parallel processing on Exadata storage cells along with high speed Infiniband network interfaces. The environment also supports GoldenGate, enabling real-time data integration.

Depending on the machine size, the database servers and storage cells can be configured in a number of ways to provide more than one RAC cluster. If your source and target database reside in the same database machine, there is no need to configure a data pump process. Data can be transmitted directly from Extract to Replicat at very high speeds. This applies to Exadata and nonExadata environments.

Supported compression methods

Oracle Exadata includes a unique compression method that enables enhanced performance with huge data compression, known as Hybrid Columnar Compression. With integrated capture mode enabled, Oracle GoldenGate 12c supports all the following compression types:

  • The basic compression
  • The OLTP compression
  • Exadata Hybrid Columnar Compression (EHCC)

Considerations

Configuring GoldenGate on Exadata is similar to other RAC environments that require a shared mount point to support persistent GoldenGate files. We have previously mentioned ACFS as a shared filesystem, which is now supported in Exadata environments that run Grid Infrastructure version 12.1.0.2 or higher. However, in our example, we will use DBFS.

As previously stated, the GoldenGate Manager process must only run on one node in the RAC cluster. To prevent Extract and Replicat processes from being started concurrently, mount DBFS on a single RAC node to deny access to the checkpoint files from other nodes. To enable automatic mounting of the filesystem on reboot, add the mount point detail to the node's /etc/fstab file.

Here is an example:

/sbin/mount.dbfs#/@DBConnectString /mnt/oracle/dbfs fuse rw,user,noauto 0 0

Ensure that GoldenGate is installed on each node in the cluster and that the parameter files exist in all the local subdirectories. Checkpoint, bounded recovery, temporary, and trail files must reside on the DBFS. It is best practice to configure the Oracle wallet and Credential Store and have these files also placed on the shared storage.

Creating the Extract process

The following steps guide us through the creation of the Extract process on the source database using DBFS that will store the trail files:

  1. Ensure that the DBFS filesystem is already mounted. As the root user, create the dirchk, dirdat, and dirtmp GoldenGate subdirectories on top of the mount point (/mnt/oracle/dbfs). Here is an example:
    mkdir /mnt/oracle/dbfs/ogg/dirchk
mkdir /mnt/oracle/dbfs/ogg/dirdat
mkdir /mnt/oracle/dbfs/ogg/dirtmp
  2. As root, grant the oracle user read/write privileges to the ogg directory:
    chown –R oracle:oinstall /mnt/oracle/dbfs/ogg
  3. As the oracle user, remove the GoldenGate subdirectories: dirchk, dirdat, and dirtmp from the GoldenGate Home on each node in the cluster:
    rmdir $OGG_HOME/dirchk
rmdir $OGG_HOME/dirdat
rmdir $OGG_HOME/dirtmp
  4. Now, create symbolic links to the newly created DBFS mount point directories on each node in the cluster:
    cd $OGG_HOME
ln –s /mnt/oracle/dbfs/ogg/dirchk dirchk
ln –s /mnt/oracle/dbfs/ogg/dirdat dirdat
ln –s /mnt/oracle/dbfs/ogg/dirdat dirtmp
  5. Now that the DBFS mount point and GoldenGate subdirectories are created on the shared filesystem, we can register the Extract with the database first and then create the Extract process group. Finally, add the EXTTRAIL to the process.

Creating the Replicat process

Now that the DBFS mount point and GoldenGate subdirectories have been created on the shared filesystem, we can create the Replicat process:

  1. Firstly, create a Replicat parameter file using the EDIT PARAMS command in GGSCI. The discard directory need not be on the shared DBFS filesystem because these files are not required for the process recovery of GoldenGate.
  2. Now, create the Replicat process. Note that when not configuring a data pump process, the Replicat uses the same EXTTRAIL as the source.
  3. Start the GoldenGate process.
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