> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/ha-and-performance/optimization-and-tuning/query-optimizer/optimizer-trace/how-to-collect-large-optimizer-traces.md).

# How to Collect Large Optimizer Traces

[Optimizer traces](/docs/server/ha-and-performance/optimization-and-tuning/query-optimizer/optimizer-trace.md) can be large for some queries.

In order to collect a large trace, you need to perform the following steps (using 128 MB as an example):

```
set global max_allowed_packet=128*1024*1024;
```

Reconnect specifying `--max-allowed-packet=128000000` for the client as well.

```
set optimizer_trace=1;
set optimizer_trace_max_mem_size=127*1024*1024;
```

Now, one can run the query and save the large trace.

## See Also

* [optimizer\_trace](/docs/server/server-management/variables-and-modes/server-system-variables.md#optimizer_trace) system variable
* [optimizer\_trace\_max\_mem\_size](/docs/server/server-management/variables-and-modes/server-system-variables.md#optimizer_trace_max_mem_size) system variable
* [max\_allowed\_packet](/docs/server/server-management/variables-and-modes/server-system-variables.md#max_allowed_packet) system variable

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