AD9361 AGC fast attack mode

Hi,

   I am using AD9361 for my application. In the beginning, the ADI engineers gave me a config list which used MGC mode and the FGPA could receive the right data, Now, I want to change to AGC fast attack mode. When I set the to AGC mode and gain table mode , is there any need to set the gain index? Will AGC gain index pointer point to the right gain index automatically?