On 2017-11-27, at 12:42:56, Ed Jaffe wrote:

> On 11/27/2017 11:22 AM, John McKown wrote:
>> ​BDAM is a "traditional" access method, like BSAM. So it cannot be _easily_ 
>> used by
>> AMODE(31),RMODE(31) programs.
> 
> Whaaaat?! AMODE(31) callers were supported by the very, very first release of 
> DFSMS!
> 
> Gosh I can't remember how many decades ago that was, but it's been a long, 
> long time...
>  
Can all the data areas; DCB, exits, DECB, IOB, Buffers, ... reside above the 
line?

How much recoding of a 370 program is needed to support this?

In days of yore, when I was trying to support both 370 and XA, I found it
simplest to keep all the I/O stuff below the line and call a 31-bit interface
interface routine which set AMODE 24 and branched to 24-bit code.

-- gil

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