ARR's are only required by PC-ss and then too, only if they're entered in an enabled and unlocked task mode. Don't think we had them back then, hence FRR's.
Aside from that, FRR's are LIFO and I believe (though I cannot remember them of the top of my bald head) there are TCB flags that indicate their presence. Kind Regards Jim Thomas 617-233-4130 (mobile) 636-294-1014 (res) [email protected] (Email) -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of michealbutz Sent: Sunday, July 17, 2011 4:00 PM To: [email protected] Subject: Re: Explination of EUT/FRR Didn't realize the that color was removed when the message was sent Here are my questions Thanks in Advance FRR information is stored off of PSA - not in any task related block. Statement. As opposed to a SCB Thus the routine FRR can be called by a SRB or TCB since PSA is related to the CPU Question What if there is a CPU switch in the routine being protected by the FRR When DAS came out (MVS/SP1.3) ESTAE could not operate in other than primary=home=secondary. The only way a PC routine could do recovery was thru an FRR. Rather than require that these routines get a lock to be protected, a secondary FRR stack was created and a bit in PSA that indicated that an EUT FRR stack was active. Then, if there is a task switch, the EUT FRR stack is saved and restored upon redispatch. Question I thought PC routines are protected by a ARR Question Going back to the first comment if EUT FRR are per TASK how does the Z/OS know they are the secondary since all FRR's Are Created by SETFRR -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of michealbutz Sent: Sunday, July 17, 2011 4:48 PM To: [email protected] Subject: Re: Explination of EUT/FRR Questions in RED -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Binyamin Dissen Sent: Sunday, July 17, 2011 4:17 PM To: [email protected] Subject: Re: Explination of EUT/FRR On Sun, 17 Jul 2011 15:45:30 -0400 michealbutz <[email protected]> wrote: :> I have seen these terms EUT Enabled Unlocked Task /FRR and this my understanding :> I ASSUME Enabled means Enabled for I/O interrupts BIT 6 of Psw the only way I know how :>to set this is with the LPSW inst Also External. IOW not subjected to be interrupted by something external. :> Unlocked means not holding a Lock Holding a Lock means using some Flavor of the :>SetLock :> Task means running in Task Mode as opposed to a SRB :> When the Term FRR is appended it means this unit of work is protected by a FRR More of a historical thing. FRR information is stored off of PSA - not in any task related block. As opposed to a SCB Thus the routine FRR can be called by a SRB or TCB since PSA is releated to the CPU What if there is a CPU switch in the routine being protected by the FRR When DAS came out (MVS/SP1.3) ESTAE could not operate in other than primary=home=secondary. The only way a PC routine could do recovery was thru an FRR. Rather than require that these routines get a lock to be protected, a secondary FRR stack was created and a bit in PSA that indicated that an EUT FRR stack was active. Then, if there is a task switch, the EUT FRR stack is saved and restored upon redispatch. I thought PC routnes are protected by a ARR Going back to the first comment if EUT FRR are per TASK how does the Z/OS know they are the secondary since all FRR's Are Created by SETFRR A key zero routine in any environment (TCB/SRB, any address spaces) can define an EUT FRR. Of course, if the routine was in TASK mode this does add restrictions (one the EUT FRR is established no SVCs, etc.) but if the routine does not know how it is being called and does not need the services this is an easy way to go. -- Binyamin Dissen <[email protected]> http://www.dissensoftware.com Director, Dissen Software, Bar & Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. 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