This means Redis has hit its memory limit and the current eviction policy will not free space, so it rejects writes. Changing the policy or freeing memory resolves it. Jump to your situation below or work through the methods in order.
The Redis OOM command not allowed when used memory > 'maxmemory' error means Redis has reached its configured memory limit and the active eviction policy will not free space, so it refuses any command that would use more memory. The default policy noeviction returns this error on writes once the limit is hit. The fix is to choose how Redis should behave when full: set a sensible eviction policy such as allkeys-lru so it evicts the least-recently-used keys automatically, raise maxmemory or add RAM if the dataset genuinely needs more room, and free memory by deleting unused keys or setting expirations. Investigating what is consuming memory (large keys, no TTLs) prevents it recurring. Once Redis can either evict or has headroom, writes succeed again.
Redis keeps everything in memory and enforces a maxmemory ceiling. When usage reaches that ceiling, what happens next depends on the eviction policy. With the default noeviction, Redis protects your data by refusing writes rather than dropping keys, which surfaces as the OOM error.
So the error is really a policy decision, not a crash. Either you let Redis evict old data automatically by choosing an eviction policy, or you give it more room with a higher maxmemory or more RAM, or you reduce what is stored. Which path fits depends on whether the data is a cache (evict freely) or a store of record (add room).
“OOM is Redis hitting its memory ceiling and, under the default noeviction policy, refusing to drop your data, so it refuses the write instead. The first question I ask is what is this Redis, a cache or a store? If it is a cache, set allkeys-lru and let it evict old keys automatically. If it is a store of record, you give it more room with a higher maxmemory or more RAM. And either way I hunt down the big keys and the keys with no TTL, because that is usually what filled it.”
CONFIG SET maxmemory-policy allkeys-lru
CONFIG SET maxmemory 4gb
EXPIRE mykey 3600
INFO memory redis-cli --bigkeys
OOM is Redis at its memory limit with noeviction refusing writes. For a cache, set maxmemory-policy to allkeys-lru so it evicts automatically. For a store of record, raise maxmemory or add RAM. Either way, find the big keys and add TTLs so memory does not fill up again.
If memory stays full even after eviction, check for a large replication backlog, AOF rewrite buffers, or client output buffers in INFO memory, since those consume memory outside your keys and can keep Redis at the ceiling. You can also submit your error to us for a tailored fix.
