AH00288: scoreboard is full, not at MaxRequestWorkers Nginx / Apache Origin: Edge & web server OSI layer 7 · Application Last updated 5 Nov 2026

Apache: [mpm_event:error] AH00288: scoreboard is full, not at MaxRequestWorkers. Increase ServerLimit

The shared scoreboard (process table) has no free slot even though the request limit isn't reached.

Exact message you may see AH00288: scoreboard is full, not at MaxRequestWorkersscoreboard is full, not at MaxRequestWorkers. Increase ServerLimit[mpm_event:error] AH00288: scoreboard is fullAH00288 scoreboard full Apachenot at MaxRequestWorkers Increase ServerLimit
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Seen on: Apache Linux

Meaning

Increase ServerLimit (and ThreadLimit/ThreadsPerChild) so ServerLimit × ThreadsPerChild ≥ MaxRequestWorkers. Common when MaxRequestWorkers was raised above the default limits without raising ServerLimit. Restart (not reload) after changing.

Common causes

  • MaxRequestWorkers raised without ServerLimit
  • Too many processes with few threads
  • Event MPM defaults
  • Stuck/graceful-stopping children holding slots
  • Reload after config limits changed

⚡ Quick fix

  1. Set ServerLimit ≥ MaxRequestWorkers / ThreadsPerChild
  2. Full systemctl restart apache2
  3. Check for stuck workers in server-status

Detailed fix by platform

Apache

  1. <IfModule mpm_event_module> ServerLimit 16 ThreadsPerChild 25 MaxRequestWorkers 400 </IfModule>

How to diagnose

  1. Limits — ServerLimit × threads?
  2. Restart — Full?
  3. Children — Stuck?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Edge & web server. Errors that are often confused with or caused by this one (click to open):

103 — HTTP 103 Early Hints (HTTP)1031200 — Cloudflare Error 1200: Cache connection limit (Cloudflare)1200304 — HTTP 304 Not Modified (HTTP)304504 — HTTP 504 Gateway Timeout (HTTP)504524 — Cloudflare Error 524: A Timeout Occurred (Cloudflare)524AH00015: Unable to open logs — Apache: AH00091: apache2: could not open error log file /var/log/apache2/error.log. AH00015: Unable to open logs (Permission denied) (Nginx / Apache)AH00015: Unable to op…AH00037: Symbolic link not allowed or link target not accessible — Apache: [core:error] AH00037: Symbolic link not allowed or link target not accessible: /var/www/html/current (Nginx / Apache)AH00037: Symbolic lin…AH00072: make_sock: could not bind to address 0.0.0.0:80 — Apache: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:80 / AH00015: Unable to open logs (Nginx / Apache)AH00072: make_sock: c…AH00288: …

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