What is Windows Error DB-MONGODB-OUTOFMEMORY-021 (MongoDB Out Of Memory (Error 21))?

Error DB-MONGODB-OUTOFMEMORY-021 (MongoDB Out Of Memory (Error 21)) is a Windows General System error that occurs when mongodb: the database ran out of memory. increase buffer pool size or add more ram.. This guide provides step-by-step solutions to resolve this issue.

What causes Error DB-MONGODB-OUTOFMEMORY-021?

A running application has a memory leak consuming all available RAM. The system page file (virtual memory) is too small or disabled. Too many applications are running simultaneously. A driver is consuming excessive kernel memory (nonpaged pool)

How do I fix Error DB-MONGODB-OUTOFMEMORY-021 (MongoDB Out Of Memory (Error 21))?

Increase Virtual Memory (Page File): Press Win+R, type sysdm.cpl, press Enter. Go to Advanced tab → Performance Settings → Advanced → Virtual Memory → Change. Uncheck 'Automatically manage paging file size'. Select your system drive, choose 'Custom size'. Set Initial size to 1.5x your RAM, Maximum to 3x your RAM (e.g., 12288 / 24576 for 8GB RAM). Click Set → OK → Restart your computer

Fix MongoDB Out Of Memory (Error 21) — Windows Error Code DB-MONGODB-OUTOFMEMORY-021

🎮 Common Scenario: Are you experiencing Error DB-MONGODB-OUTOFMEMORY-021 while launching or installing AutoCAD? The solutions below directly address the system interactions specific to this application.

⚡ Quick Fix

Increase Virtual Memory (Page File): Press Win+R, type sysdm.cpl, press Enter

👇 See all 3 solutions below

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📑 Table of Contents

What is Error DB-MONGODB-OUTOFMEMORY-021? Common Causes Step-by-Step Solutions Prevention Tips Related Errors

💡 What is Error DB-MONGODB-OUTOFMEMORY-021?

Windows System Error Code DB-MONGODB-OUTOFMEMORY-021, known as MongoDB Out Of Memory (Error 21), is a General System error that occurs during core Windows operations. The error indicates that: MongoDB: The database ran out of memory. Increase buffer pool size or add more RAM. When this error is encountered, the Windows operating system was unable to complete the requested operation within the system services subsystem. The error code DB-MONGODB-OUTOFMEMORY-021 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name MongoDB Out Of Memory (Error 21) maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within core Windows operations is essential for effective troubleshooting.

⚠️ Common Causes

A running application has a memory leak consuming all available RAM
The system page file (virtual memory) is too small or disabled
Too many applications are running simultaneously
A driver is consuming excessive kernel memory (nonpaged pool)

✅ Step-by-Step Solutions

1 Increase Virtual Memory (Page File)

Press Win+R, type sysdm.cpl, press Enter
Go to Advanced tab → Performance Settings → Advanced → Virtual Memory → Change
Uncheck 'Automatically manage paging file size'
Select your system drive, choose 'Custom size'
Set Initial size to 1.5x your RAM, Maximum to 3x your RAM (e.g., 12288 / 24576 for 8GB RAM)
Click Set → OK → Restart your computer

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Show Advanced Solutions (2 more)

2 Identify Memory-Hungry Processes

Press Ctrl+Shift+Esc to open Task Manager
Click 'More details' if needed, then sort by Memory column
Identify processes using excessive memory (>1GB is suspicious)
Right-click the process → End Task (save your work first)
If a process consistently leaks memory, check for updates or reinstall it

3 Check for Memory Leaks with RAMMap

Download RAMMap from Microsoft Sysinternals (free tool)
Run RAMMap and check the 'Use Counts' page for unusually large allocations
If 'Nonpaged Pool' is very large, a driver has a memory leak
Run: poolmon.exe to identify which driver tag is consuming pool memory
Update or uninstall the offending driver

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How To Fix Out Of Memory Error Windows 10 11

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💻 Diagnostic Command

Run this PowerShell command to find related events in your system log:

Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*DB-MONGODB-OUTOFMEMORY-021*" -or $_.Message -like "*MongoDB Out Of Memory (Error 21)*"} | Format-List

💡 Open PowerShell as Administrator, paste the command above, and press Enter.

🛡️ Prevention Tips

Monitor memory usage with Task Manager and set alerts for >85% usage
Keep your page file on an SSD for faster virtual memory performance
Close unused browser tabs and applications before running heavy software

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Last updated: 2026-03-13

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Based on Official Microsoft Documentation

Solutions Tested on Windows 10 & 11

Error codes sourced from Microsoft Win32 SDK. Updated 2026-03-13.