What are the Rules recommended by SAP for User Ids?

Hello All,

Good Evening.

What are the parameters that I need to consider for proposing SAP User Ids in Implementation Project? I could see that newly installed SAP system allows spaces also for username.

Could you please suggest me on below questions

1. User Id naming convention?

2. Min and Max length of SAP User Ids, and Where can I define these parameters?

3. No spaces and Special Characters should be allowed(what need to be set up to achieve this)

Please help me with the implementation plan, if you already have any on user Id design...

Thanks in advance..

Regards,

Ch.