KB-2404 Application Server Restart When Viewing Process History for Instances With Very Large Process Variables
Symptoms
- Application server crashes when a user opens the Process History diagram of a specific process instance.
- Site slowness or unresponsiveness
Cause
When the Process History diagram is loaded, the engine retrieves all history records for the instance before paging. If the instance contains a very large process variable (commonly a list-type PV repeatedly appended to, or a PV that has grown to hundreds of MB / several GB), generating these history entries becomes extremely memory and CPU-intensive, exhausting heap.
Action
There is no action or workaround currently available for this issue. If you are facing this issue, please open a support case with Appian to identify the problematic instance.
Workaround
- Avoid opening the Process History diagram for instances known or suspected to have very large process variables. Simply viewing history can trigger or worsen the condition.
- Mark large or unnecessary process variables as Hidden, which excludes them from process history and reports. See the Process Model Variables tab documentation (Hidden flag).
- Prevent unbounded PV growth in design — avoid infinite/uncontrolled appends to list-type variables; add bounds or offload large data to a data store.
Affected Versions
This article applies to all versions of Appian.
Last Reviewed: September 2026