Assessing disk space and memory requirements

CDC Replication requires disk space and memory when it processes change data from your source database. In order to process change data efficiently and replicate these changes to your target system, it is very important that CDC Replication has adequate disk space and memory for each of the components described.

Memory requirements for the JVM (Java Virtual Machine)

As a Java-based product, CDC Replication requires you to allocate the maximum amount of memory (RAM) to be used by the Java™ Virtual Machine (JVM). This prevents CDC Replication from using all of the available memory on the system where it is installed.

The Maximum Memory Allowed value is set on a per-instance basis for each instance you create for your target database. In most cases the default values are adequate. However, if your database is processing an extremely heavy workload, you may have to adjust the default values. The RAM allocated must be physically available on your system.

Disk space requirements for the global disk quota

Disk space is required on your target system for this quota which is used to store in-scope change data that has not been committed in your database. The amount of disk space required is determined by your replication environment and the workload of your source database.

You can configure the amount disk space that is allocated to this quota with the mirror_global_disk_quota_gb system parameter. The default setting of this system parameter is such that CDC Replication will only stop replicating after this disk quota exhausts all available disk space on your system. If you would prefer CDC Replication to stop replicating after it uses a specific amount of disk space, you can specify the value with this system parameter in Management Console.