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I have been doing some work on this article and noticed that this article overlaps Channel I/O and, to some extent Count key data. The latter is strictly DASD, while it seems like the former should be less IBM-centric. On the other hand the topic of this article is the EXCP macro, and perhaps not the internals of CCWs. There seems to be no place where the CCW information fits well, but perhaps Channel I/O and Count key data have too much detail. I think we need another article to consolidate System/360 (and later) I/O processing and strip the excess out of these three articles. I don't know what such an article should be called. Peter Flass ( talk) 16:18, 6 December 2019 (UTC)
The title of the article is generic, but EXCP exists in DOS/360 and successors and many of the details are quite different from those for OS/360 and successors. I've added some DOS reference, split the existing references depending on whether they are generic, OS-specific or DOS-specific, and added a warning to the lead. If there is an editor with DOS experience, please consider writing DOS-specific sections. Shmuel (Seymour J.) Metz Username:Chatul ( talk) 20:55, 18 December 2019 (UTC)
As well as I understand it, from reading Mythical Man Month some years ago, the way OS/360 came out, and specifically the I/O subsystem, had to do with the way quotas were used for the people writing it. There were limits in how much supervisor memory space could be used, resulting in as much as possible being moved into user space. Least obvious might be the DCB. In any case, the whole idea behind EXCP is that the access methods do much of their work in user space and problem state, and build the appropriate channel program. Then EXCP where the OS verifies that the channel program doesn't do things it isn't supposed to do, like read/write the wrong data set, or wrong part of memory. As well as I know, Unix and related systems do much more in system space and supervisor state. Enough that Unix reports time used by programs as both user and system time. I don't know that all needs to be in the article, but access methods writing channel programs for user programs should be, and probably the indication that it is done in user space and problem state. A side effect of writing the OS that way, is that user programs can avoid access methods, write their own channel programs, and EXCP them. Then there are self-modifying channel programs, and never-ending channel programs, that might be discussed somewhere. Gah4 ( talk) 19:36, 26 May 2020 (UTC)
![]() | This article is rated Stub-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||
|
I have been doing some work on this article and noticed that this article overlaps Channel I/O and, to some extent Count key data. The latter is strictly DASD, while it seems like the former should be less IBM-centric. On the other hand the topic of this article is the EXCP macro, and perhaps not the internals of CCWs. There seems to be no place where the CCW information fits well, but perhaps Channel I/O and Count key data have too much detail. I think we need another article to consolidate System/360 (and later) I/O processing and strip the excess out of these three articles. I don't know what such an article should be called. Peter Flass ( talk) 16:18, 6 December 2019 (UTC)
The title of the article is generic, but EXCP exists in DOS/360 and successors and many of the details are quite different from those for OS/360 and successors. I've added some DOS reference, split the existing references depending on whether they are generic, OS-specific or DOS-specific, and added a warning to the lead. If there is an editor with DOS experience, please consider writing DOS-specific sections. Shmuel (Seymour J.) Metz Username:Chatul ( talk) 20:55, 18 December 2019 (UTC)
As well as I understand it, from reading Mythical Man Month some years ago, the way OS/360 came out, and specifically the I/O subsystem, had to do with the way quotas were used for the people writing it. There were limits in how much supervisor memory space could be used, resulting in as much as possible being moved into user space. Least obvious might be the DCB. In any case, the whole idea behind EXCP is that the access methods do much of their work in user space and problem state, and build the appropriate channel program. Then EXCP where the OS verifies that the channel program doesn't do things it isn't supposed to do, like read/write the wrong data set, or wrong part of memory. As well as I know, Unix and related systems do much more in system space and supervisor state. Enough that Unix reports time used by programs as both user and system time. I don't know that all needs to be in the article, but access methods writing channel programs for user programs should be, and probably the indication that it is done in user space and problem state. A side effect of writing the OS that way, is that user programs can avoid access methods, write their own channel programs, and EXCP them. Then there are self-modifying channel programs, and never-ending channel programs, that might be discussed somewhere. Gah4 ( talk) 19:36, 26 May 2020 (UTC)