Darksage,
If the service member has been determined to be unfit by reason of disability that is found to be of a permanent nature and have been rated at 30% or greater, or if rated at less than 30% but have 20 or more years of service, they will be placed on the PDRL under authority of 10 USC 1201 or 1204. This is a permanent status.
Retired pay is computed under the same two methods stated in the TDRL section above, with the exception of the 50% minimum. A member of the TDRL whose disability is now considered to be of a permanent nature will be transferred to the PDRL and the retired pay is computed using the same retired pay base utilized while on the TDRL and the new percentage (no longer a 50% minimum). Therefore your pay will be calculated at the time of retirement and any subsequent pay increase will be Cost of Living Allowances. Hope this helps answer your question.
fdm