[in] Render targets are not lockable unless the application specifies TRUE for Lockable. Note that lockable render targets reduce performance on some graphics hardware.
Discard
[in] Set this flag to TRUE to enable z-buffer discarding, and FALSE otherwise.
If this flag is set, the contents of the depth stencil buffer will be invalid after calling either IDirect3DDevice9::Present or IDirect3DDevice9::SetDepthStencilSurface with a different depth surface.