# OpenTelemetry Metrics Limitations

When sending data from your application via OpenTelemetry, the following limits and limitations apply.

## Limits

Entity | Limit | Description |
---|---|---|

Metric key length, characters | Min: 3, Max: 250 | The minimum and maximum total length of a metric key. If a metric key is longer than the maximum length, the metric key is truncated to 250 characters. If a metric key is shorter than 3 characters, the metric key is padded with underscore characters to make it reach the minimum requirement (for example, `a` becomes `a__` ). |

Dimension key length, characters | Min: 1, Max: 100 | The minimum and maximum total length of a dimension key. If the maximum length is exceeded, the dimension key is truncated to 100 characters. |

Dimension value length, characters | 255 | The maximum total length of a dimension value. If the maximum length is exceeded, the dimension value is truncated to 255 characters. |

Number of dimensions per metric data point | 50 | The maximum total number of dimensions in a single metric data point. If the number of dimensions is exceeded, the whole data point is dropped. |

Total number of possible metric keys per environment | 20,000 | The maximum number of metric keys that can be registered in Dynatrace. |

Number of tuples per month per metric | 1,000,000 | The maximum number of tuples (unique metric-dimension key-value type combinations) for each metric key for the last 30 days. |

Number of tuples per month for all custom metrics | 50,000,000 | The maximum number of tuples (unique metric-dimension key-value type combinations) for all custom metrics for the last 30 days. |

Instrument unit, characters | 63 | The maximum total length of the instrument unit. If the maximum length is exceeded, the unit is dropped. |

Instrument description, characters | 1023 | The maximum total length of the instrument description. If the maximum length is exceeded, the instrument description is truncated to 1023 characters. |

## Limitations

### Metric keys

- A metric key consists of sections separated by dots (for example,
`dt.metrics`

). - A metric key can contain lowercase and uppercase letters, numbers, hyphens (
`-`

), and underscores (`_`

). - A metric key must start with a letter character.
- A metric key must
**not**contain non-Latin characters (such as`ä`

,`ö`

, and`ü`

). - A metric key may be suffixed automatically depending on the payload (for example,
`.count`

for counters and`.gauge`

for gauges)

If you use characters that are invalid according to the rules above, they will be **replaced with underscores**.

If your metric key does not have at least one valid character, the data point will be dropped.

### Dimension keys

- Dimensions are comparable to span or resources attributes.
- A dimension key can contain only lowercase letters (
**not**uppercase letters), numbers, hyphens (`-`

), periods (`.`

), and underscores (`_`

). - A dimension key must start with a letter character.
- A dimension key must
**not**contain non-Latin characters (such as`ä`

,`ö`

, and`ü`

). - A dimension key can be in the
`key.key-section`

format. - You can specify up to 50 dimensions.
- If the same dimension key is specified multiple times in a single payload, only the value that occurs first is accepted.

If you use characters that are invalid according to the rules above, they will be **replaced with underscores**.

If your dimension key does not have at least one valid character, the key will be dropped.

Dimension values must be passed as a **string**, **boolean**, or **integer**.

Dynatrace does not support non-string dimensions and will convert booleans and integers to strings upon ingest.

If any other type is used, the entire dimension will be dropped.