Redis: 'OOM Command Not Allowed When Used Memory > maxmemory'

Redis hit its memory cap and the eviction policy is 'noeviction' — so writes fail. Pick a policy and stop storing unbounded keys without TTLs.

What you'll see

Writes fail with the OOM error; reads still work
Used memory pinned at maxmemory in INFO memory

Root causes

Eviction policy is noeviction

The default on some distros: when full, Redis refuses writes rather than evicting.

Keys with no TTL accumulating forever

Sessions, job queues, and rate-limit counters written without EXPIRE grow unbounded.

Fix it

Check the current policy and memory

redis-cli CONFIG GET maxmemory* | head; redis-cli INFO memory | grep used_memory_human

Set a cache-appropriate policy (config AND runtime)
```
redis-cli CONFIG SET maxmemory-policy allkeys-lru
```
Find key classes without TTLs
```
redis-cli --bigkeys; redis-cli DBSIZE
```
Add TTLs at write time
```
SET session:abc data EX 3600
```

Field note

allkeys-lru for pure cache, volatile-lru if some keys must survive. Never noeviction for a cache tier — that setting is for durable stores you babysit.

Common questions

Why did Redis stop accepting writes?

maxmemory is reached and the policy is noeviction: Redis refuses writes rather than delete data. Check INFO memory (used_memory vs maxmemory_human) and pick a policy appropriate to your use — allkeys-lru for caches, noeviction only when eviction would lose real data.

Which eviction policy should a cache use?

allkeys-lru for general caches (evicts least-recently-used keys, any key eligible); volatile-lru only when some keys must never be evicted (mark the rest with TTLs). noeviction on a cache just moves the failure into your app.

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Redis: 'OOM Command Not Allowed When Used Memory > maxmemory'

What you'll see

Root causes

Eviction policy is noeviction

Keys with no TTL accumulating forever

Fix it

Field note

Common questions

Related fixes

Ship it right the first time

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