No. ZAP field,=PL1'0' MVC FIELD+4(256),FIELD etc.
The length goes on the first operand. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 עַם יִשְׂרָאֵל חַי נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר ________________________________________ From: IBM Mainframe Assembler List <[email protected]> on behalf of Robin Vowels <[email protected]> Sent: Sunday, November 30, 2025 4:55 AM To: [email protected] <[email protected]> Subject: Re: quick way to initialize Packed fields? External Message: Use Caution On 2025-11-30 14:34, Brian Westerman wrote: > Hi, > > I have a program in which I have 104 PL4 fields tht are used for > various counters, and when the program starts it spends a significant > amount of time initializing all of those fields to zero. > > we used to use ZAP field,=PL4'0' and then I found an entry (on the web) > that said it would be "slightly" faster to use MVC, so I changed it to > 104 MVC filed,=PL4'0'. > > Is there not a quicker way to do this? I know that I can ripple the > first byte of a field for up to 256 bytes with a single instruction, > but can that same type of thing be done with a 4 byte packed field? ZAP field,=PL4'0' MVC FIELD+4,FIELD(252) etc > If not, is there a quicker way to initialize these fields without doing > each one separately? > > Thanks for any tips. > > Brian
