# volumes::create_capacity

> Tag 6: a client asks how large a volume it could create; the server sends exactly one response carrying the largest size, in bytes, of a volume the client could create at that time, or an error, and the scope finishes; the answer reserves nothing.

Canonical: https://provider.diverge.network/2.3.0/endpoints/volumes-create-capacity/
Specification revision: 2.3.0

A client opens the scope with a request whose payload is the tag byte
`6` and nothing more. The server sends exactly one response, which
carries either a number of bytes or an error. The response finish
follows the response, and no frame follows the finish.

- **The request.** The request carries no parameter; the tag is the
  whole of it. [Request](/2.3.0/endpoints/volumes-create-capacity/request/)
  states its form.
- **The capacity.** The number is the largest size, in bytes, of a
  volume that the client could create by a
  [volumes::create](/2.3.0/endpoints/volumes-create/) request at the time
  of the response. It is the size of the largest single volume the
  server could make for the client, and not the sum of the server's
  room. The number `0` states that the client can create no volume at
  the time of the response.
  [Response](/2.3.0/endpoints/volumes-create-capacity/response/) states its
  form.
- **No reservation.** The answer is a fact about the time of the
  response and reserves nothing. A `volumes::create` request stating
  a size not greater than the number answered may be answered with
  insufficient capacity when the room has been taken between the two
  responses. A `volumes::create` request stating a size greater than
  the number answered, made while the capacity is unchanged, is not
  answered with the byte `0`.
- **The client.** The client is the identity under which the
  connection was authorized, as [Authorization](/2.3.0/authorization/)
  provides. The number is the capacity available to that identity.
- **The error.** An error states that the server did not answer the
  question, and that nothing was determined about the capacity. An
  error is not the number `0`.