ASVT is being allocated over the 16MB line(31 bit address).
IBM has included this option in release 3.1.0 of the z/OS operating system where the ASVT address can be loaded as 31 bit or 24 bit.
This value (CBLOC VIRTUAL31(IHAASVT)) is set in the SYS1.PARMLIB(DIAGxx) member.
File Master Plus, release 12
z/OS 3.1 and the ASVT parameter
File Master Plus is not affected based on the ASVT parameter setting.