Continuous Capture commands

Continuous Capture is a product feature that is designed to accommodate those replication environments in which it is necessary to separate the reading of the database logs from the transmission of the logical database operations.

This is useful when you want to continue processing log data even if replication and your subscriptions stop due to issues such as network communication failures over a fragile network, target server maintenance, or some other issue. You can enable or disable Continuous Capture without stopping subscriptions.

Continuous Capture allows you to avoid spikes in your source system CPU resource utilization by continuing to process log data (and write to disk as necessary) even when subscriptions are stopped. This feature allows you to avoid situations where the product uses no CPU when subscriptions are stopped and high CPU when you start subscriptions after a prolonged target system outage.

This functionality comes with the trade-off of additional disk utilization on the source machine in order to accumulate changes from the database log file when these are not being replicated to the target machine. These trade-offs should be evaluated and understood before deciding to use this feature in your replication environment. For performance reasons, if you choose to use Continuous Capture, you need to ensure that the disk where the CDC Replication staging store is located consists of very high speed disk with sufficient number of disk heads to ensure throughput.

To use the commands in this section that are applicable to Continuous Capture, you must set the staging_store_can_run_independently system parameter to false. The default value for this parameter is true.