Hi Poornima! I'm not sure what you're doing to activate this error, but here's a guide that may help: Understanding Workspaces and Lead Partitions - Marketo Docs - Product Docs
It basically separates your Marketo instance into different sections if you have teams that won't be sharing assets. Some examples of its uses are included in that doc. It's recommended to contact support if you'd like to set up a workspace because it's not necessarily needed, though I believe it's an additional cost (someone please correct me if I'm wrong).
I believe workspaces are only available in certain editions of Marketo. I would recommend reaching out to your Marketo accountmanager for more information on this.
i set the workspace as default.
This value works for production url and for test url fails.
what else can i set ?
is there any api to read the available work spaces ?
It sounds like you are attempting to use a WS with the API. If you do not have WS for your Marketo instance, then this will fail. It is not necessary to set the Default WS if you do not have more than one anyway.
See Admin> Lead Partitions and Workspaces. If you cannot see this, you do not have it.