>>>Speaking about Maintenance plan. Who makes it (if such term can apply to it)? the DBA or developer?
>>
>>DBA of course.
>>That is their job to Maintenance the databases.
>
>Thank you. I am sorry that I am asking so many questions. But what does a developer tell the DBA? That is, should the developer provide some kind of paper documentation describing what tables or what indexes it should have?

Developer can propose a table schema (with indexes) to a DBA and DBA then will implement it (and may improve).

But actually the process of DBA and Developers communications may vary from organization to organization.