OOM error

Redis has reached its memory limit and can't make room for new data.

Redis returns this error when it has reached its memory limit and can't free memory for the command. The limit is the maxmemory setting. Commands that add data fail, but commands that read or delete data still work. OOM stands for out of memory.

OOM command not allowed when used memory > 'maxmemory'.

In redis-py, this error is OutOfMemoryError: command not allowed when used memory > 'maxmemory'.

A Lua function, or a script that starts with a #!lua line, gets the same error before it starts, unless it has the allow-oom or no-writes flag. A script without that line gets the error when it calls a command that adds data, with the script's details added to the end.

Example

> SET newkey "value"
(error) OOM command not allowed when used memory > 'maxmemory'.
> GET oldkey
"value"

How to fix it

First, check how much memory Redis uses with INFO memory. Compare used_memory_human with the limit in maxmemory_human, and look at maxmemory_policy. The policy decides what Redis does when it reaches the limit. With the default policy, noeviction, Redis never removes keys to make room. It returns this error instead.

Then choose a fix:

• Let Redis remove keys. If you use Redis as a cache, set an eviction policy such as allkeys-lru. Redis then removes the least recently used keys to make room for new ones. See Eviction policies.
• Set expiry times on your keys. The volatile-* policies only remove keys that have an expiry time, also called a time to live (TTL). When no key has one, Redis can't free any memory and returns this error, as with noeviction.
• Raise the memory limit with maxmemory, if the machine has enough memory. See Using the maxmemory configuration directive.
• Use less memory. Delete keys you no longer need. See Memory optimization for ways to store the same data in less memory.