AMODE 31 to 64 transition for authorized program facility routines

Good afternoon,

Our security team requested a review of legacy assembler routines that invoke the Authorized Program Facility. Several modules were written in the early 2000s with AMODE 31 and RMODE 24 attributes.

Entry sequence excerpt:

assembler
RSECT
AMODE 31
RMODE 24
ENTRY AUTHCHK
         STM   14,12,12(R13)
         LR    12,15
         USING AUTHCHK,12

z/OS documentation indicates:

Programs running above the 16 MB line require AMODE 64 and appropriate linkage conventions when interfacing with 64-bit callers.

Before we schedule redevelopment, could anyone confirm whether a straightforward AMODE 64 migration is realistic for short APL-style routines, or whether a COBOL rewrite is typically more cost-effective?

Regards,
Rick

Short answer: migration is realistic if the routine has no RMODE 24 assumptions and no dependence on 24-bit control blocks. We converted two APL exits in under a sprint each.

If the module manipulates ECBs or old IEAVTAB-style structures, estimate a rewrite instead.

We completed a dependency scan. Two of five modules qualify for direct migration; three will move to COBOL per your guidance. Thank you.