> For the complete documentation index, see [llms.txt](https://docs.novacura.com/flow-connect/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.novacura.com/flow-connect/reference/reference/designer/steps/machine-step.md).
# External system
### 
A machine step is utilized to read or write data from/to other systems, or to modify variables in a application. Machine steps remain invisible to the operator, except when issues arise (e.g., receiving an error message from the ERP system). In case of an error in a machine step, the operator receives an error message and is directed back to the most recent user step.
Machine steps that potentially modify data in another system are termed non-reversible. Incoming connections to non-reversible machine steps are marked with an orthogonal line, indicating that the operator cannot use the back button in the flow client once this step has been successfully executed.
Avoid consecutive non-reversible Machine steps because each machine step is executed atomically, meaning any changes to underlying systems are committed as soon as the step is completed. Consequently, if a transaction has already been committed, the Flow Client cannot revert to the previous user step without risking data inconsistency. In such cases, the operator is forced to exit the application immediately.
For instance, in the example below (refer to the picture), if machine step B executes successfully but machine step C fails, the operator would be compelled to exit the application.
Read more about how to connect to system [here](/flow-connect/working-with-connect/connect-to-systems.md).
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://docs.novacura.com/flow-connect/reference/reference/designer/steps/machine-step.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.