You select a pool when you are creating a Thin Image pair if you are not using the P-VOL of a Thin Image pair (that is, you have selected No for Use Primary Volumes of Thin Image Pairs in the Create TI Pairs window of the Create TI Pairs wizard).
You select a pool when you are creating a Thin Image pair if you are not using the P-VOL of a Thin Image pair (that is, you have selected No for Use Primary Volumes of Thin Image Pairs in the Create TI Pairs window of the Create TI Pairs wizard).