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How to Increase the Noninteractive Desktop Heap Size in Windows

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Increasing the noninteractive desktop heap size in Windows registry can resolve Oracle-related GUI or service launch issues on Windows Server environments.

What Is the Desktop Heap?

In Windows, each desktop environment—whether interactive (like a user session) or noninteractive (like background services)—uses a memory allocation called the desktop heap. This heap stores GUI-related objects like windows, menus, and hooks. The registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems

contains a value named Windows of type REG_EXPAND_SZ, which includes a parameter called SharedSection. This parameter defines how memory is allocated for desktop heaps:

SharedSection=1024,3072,512

Means:
1024 → Heap size for interactive desktops
3072 → Heap size for system-wide shared memory
512 → Heap size for noninteractive desktops (e.g., services)

Why Oracle Needs This Change

Oracle applications—especially those using GUI components or launching multiple background services—can hit the desktop heap limit in noninteractive sessions. This often results in:

  • “Out of Memory” errors
  • Services failing to start
  • GUI components not rendering properly
  • Oracle jobs crashing when run in parallel

This is particularly common in environments running Oracle DataStage, Oracle Forms, or other middleware tools that spawn multiple processes or threads.

Increase the Third Value

To resolve these issues, increase the third value in SharedSection from 512 to 1024:

SharedSection=1024,3072,1024

This change:

  • Doubles the memory available for noninteractive desktops
  • Allows more Oracle services and background processes to run concurrently
  • Prevents GUI rendering failures in service contexts
  • Improves stability for Oracle workloads on Windows Server

Step-by-Step Instructions

✅ Step 1: Open the Registry Editor

  1. Press Win + R to open the Run dialog.
  2. Type regedit and press Enter.
  3. If prompted by User Account Control, click Yes.

Step 2: Navigate to the Registry Path

Go to the following location & You’ll see a value named “SharedSection” Windows of type REG_EXPAND_SZ.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems

Step 3: Edit the “Windows” Value

  1. Double-click the Windows entry.
  2. Look for the part that says: (Note: The third value (512) is the desktop heap size for noninteractive window stations (used by services).)
SharedSection=1024,3072,512

Change it to:

SharedSection=1024,3072,1024

Step 4: Save and Restart

  1. Click OK to save the changes.
  2. Restart your system to apply the new settings.

Important Notes

  • Backup your registry before making changes: In Registry Editor, click File > Export to save a copy.
  • Avoid setting the value too high (e.g., >2048), as it may cause system instability.
  • This change affects all services running in noninteractive sessions, not just Oracle.