# Persistence By default, the NATS Streaming Server stores its state in memory, which means that if the streaming server is stopped, all state is lost. On server restart, since no connection information is recovered, running applications will stop receiving messages and new published messages will be rejected with an `invalid publish request` error. Client libraries that support and set the `Connection Lost` handler (refer to [this](https://github.com/nats-io/stan.go#connection-status) for more information) will be notified that the connection is lost with the error `client has been replaced or is no longer registered`.\ Still, this level of persistence allows applications to stop and later resume the stream of messages, and protect against applications disconnect (network or applications crash). * [File Store](/cn/yi-chan/stan/changes/configuring/persistence/file_store.md) * [SQL Store](/cn/yi-chan/stan/changes/configuring/persistence/sql_store.md) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.natsclub.cn/cn/yi-chan/stan/changes/configuring/persistence.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.