about D3DPOOL_DEFAULT texture

Yes, anything in the DEFAULT pool will be lost. You can either use the MANAGED pool or you can reset/reload your assets after a lost device has been reset.

Thanks for your reply.

I have textures used as render target and updated every frame. So, I have to create copies of them in system RAM and update every frame in order not to lose them. Is this right?

Yes, you'll have to use ::GetRenderTargetData() if you need to persist your render target contents. Alternatively you need only remember the state necessary to re-render the exact same image after the D3DPOOL_DEFAULT resource is lost...

hth
Jack

I'm planning to develop painting program using Direct3D 9 and use Direct3D texture as layer, but the program may be slow if I have to update frequently...