UEXTERNALDB allows you to manage user-defined external databases and calculate model-independent history information.
Helius PFA has the capability to forward on to the custom Abaqus user subroutine UEXTERNALDB. In other words, you can use Helius PFA in conjunction with the Abaqus UEXTERNALDB subroutine.
The UEXTERNALDB subroutine can be used to communicate between subroutines and Helius PFA at the beginning of the analysis, at the beginning of each increment, at the end of each increment, and at the end of the analysis. Refer to the Abaqus Documentation for further details.
To use the UEXTERNALDB subroutine with Helius PFA, you need to include UEXTERNALDB with the Helius PFA subroutine build. Those instructions can be found here for Windows or here for Linux.