What does Windows error code 89 (ERROR_NO_PROC_SLOTS) mean?

ERROR_NO_PROC_SLOTS

What ERROR_NO_PROC_SLOTS means

The system or subsystem cannot start another process because no process slot is available. Process slots are a legacy representation of process-table capacity. Modern systems usually fail process creation for memory, quota, job, or handle reasons, but compatibility environments can still map those limits to this code.

Common causes

• A launcher repeatedly spawns child processes without reaping them
• A compatibility subsystem has a fixed process-table limit
• A job object or container constrains process count
• Process creation storms occur during retry or recovery

How to investigate

1. Count live and recently exited child processes
2. Check job, container, and service-manager process limits
3. Verify the parent waits for and closes child-process handles
4. Correlate creation failures with retry loops and crash frequency

Developer guidance

Use a bounded worker model and apply exponential backoff to process creation. Reap children deterministically and prevent multiple supervisors from launching the same workload.

Administrator and support guidance

List the process tree before restarting the parent. A large number of identical or defunct children identifies the likely leak or retry storm.

How this code differs from related results

This is not the same as thread exhaustion. A process slot includes separate address space and process bookkeeping.

References

• Microsoft: System error codes 0–499