Viewing latency values for a subscription

CDC Replication measures latency as the amount of time that passes between when data changes on a source table and when it changes on the target table.

About this task

For example, if an application inserts a row into the source table at 10:00 and CDC Replication applies that row to the target table at 10:15, then the latency for the subscription is 15 minutes. It is up to you to decide how much latency you are willing to tolerate in your environment.

The Latency area of the Subscriptions view of the Monitoring perspective displays a graphical summary of latency for the current subscription.

In order to view latency information, you need to ensure that Collect Statistics is enabled for the subscription. Once enabled, an icon Collect Statistics icon will be displayed in a column on the right side of the subscription list.

You can drill down in this area to see a more detailed explanation of latency by double-clicking on the area title. A summary of latency values and a graph will be displayed:

Current
Indicates the amount of time the subscription is latent in replicating data to the target.
High
Indicates the highest amount of time a subscription has experienced latency since you started to collect statistics.
Low
Indicates the least amount of time a subscription has experienced latency since you started to collect statistics.
Average
Indicates the average amount of time a subscription has experienced latency since you started to collect statistics.

You can export the latency information to a comma-delimited file by clicking Export Statistics, located above the graph.

Latency considerations
  • To receive accurate latency statistics for a subscription, ensure that your system time (for each machine where you have installed CDC Replication) is synchronized and that the time zone matches the time zone of your region. CDC Replication calculates latency based on your system time and the offset from Coordinated Universal Time (UTC).
  • Depending on the platform on which you have CDC Replication, you can set the DEADBAND PERCENTAGE system parameter to greater than zero on your target datastore if you want CDC Replication to apply padding around your latency threshold.
  • Latency can jump for idle nodes in Oracle RAC environments due to Oracle checkpoint procedures.

Procedure

  1. Click Monitoring > Subscriptions.
  2. Select a subscription.
  3. Ensure that Collect Statistics has been enabled for the subscription.
  4. Double-click on Latency.