This isn't the length, it's the address (target). I've been puzzling at this for a bit. Am I correct in concluding that OP's point is: 1) In non-AR mode, a target register of 0 means "move to location 0" (assuming non-zero input length), in the home address space, of course 2) In AR mode, it means the same, EVEN IF AR0 is set 3) OP is suggesting that it would make more sense if AR0 were honored in this case
? If so, then I can see OP's point. MVCLing to location 0 in the home address space is pretty unlikely; less so in AR mode. But...this is how it's implemented and documented, so not likely to change. And of course there are other registers that can be used to move to location 0 in AR mode, so it's not like it makes something impossible. -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Robin Vowels Sent: Tuesday, March 18, 2025 10:13 AM To: [email protected] Subject: Re: AR Mode: MVCL R0,Rx No; MVCL Rx,Ry Yes Enlighten me. What is the purpose of AR mode? Does not a length of zero mean that the content of the corresponding address register not be used? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
