# OOM error

```json metadata
{
  "schema_version": 2,
  "title": "OOM error",
  "description": "Redis has reached its memory limit and can't make room for new data.",
  "categories": ["docs","develop","stack","oss","rs","rc","oss","kubernetes","clients"],
  "tableOfContents": {"sections":[{"id":"example","title":"Example"},{"id":"how-to-fix-it","title":"How to fix it"}]}

,
  "codeExamples": []
}
```


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`](https://redis.io/docs/latest/commands/info). 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](https://redis.io/docs/latest/develop/reference/eviction#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](https://redis.io/docs/latest/develop/reference/eviction#maxmem).
- **Use less memory.** Delete keys you no longer need. See [Memory optimization](https://redis.io/docs/latest/operate/oss_and_stack/management/optimization/memory-optimization) for ways to store the same data in less memory.