Hi Jun King,
Thank you for your question,
Depending on precisely what information you need when storing the 'StreamID' from your point of view - you may want to use the following REST API endpoints with the 'StreamID' to obtain the information:
Chat Room - Infomation = https://developers.symphony.com/restapi/reference/room-info-v3
Chat Room Stream Information = https://developers.symphony.com/restapi/reference/stream-info-v2
Chat Room - Members = https://developers.symphony.com/restapi/reference/room-members
However, should you wish to pull the chat messages from the chat room conversation - you will require the 'MessageID' of each message in the conversation before you can obtain information for it using the GET Message REST API endpoint (https://developers.symphony.com/restapi/reference/messages-v4).
Symphony recommends using the Content Export feature within your Symphony Pod environment to export the Chatroom Conversation Messages via daily exports to an SFTP location - which you can than later import into your back internal systems.
For Symphony pod environments - there is a default data retention period of 12 months for all chat message history - this does also depend on the legal & complaince requirements for each company. Should you wish to store chat messages it would be recommend to use the Content Export feature as mentioned above to back up to your internal systems.
Please let me know you have any additional questions.
Kind regards