Issue
By design, the platform implements 'session synchronization', which means that for each user, the platform processes only one transaction at a time.
This is implemented to prevent a single user from causing significant instance performance issues by triggering multiple transactions concurrently and consuming a large amount of node and database resources.
Release
All releases
Resolution
For example, if a user opens multiple browser tabs simultaneously, each displaying a list, homepage, dashboard, etc., the browser tabs will load the data on each tab synchronously, one at a time. This is session synchronization in play.
How can I view session sync?
Via the Instance UI
- Filter Navigator -> 'client transaction' logs
- modify the list to add the 'session wait time' column (if it is not listed).
- Filter out the transactions for the user you are interested in, and sort the transactions in chronological order (Created).
Via the localhost log files on the application nodes
(This may help KB0997495)
If you see a user transaction with a high 'session wait', you can observe, as shown in the screenshot below, that this transaction was processed extremely quickly (0.008ms) and the SQL time is 0.001ms. The key figure here is the session wait time, which is 9.8 seconds, indicating that this transaction had to wait almost 10 seconds for the previous transaction to complete before it could execute itself.
In scenarios like this, the users of the instance need to understand how session synchronization works and be aware that this can appear to the end user as a 'slow instance'; however, this is expected behavior.
This feature exists in the platform to prevent a single user from consuming all the available resources on an application node.
