Re: Curiousity: format of an unused page dataset?
In [EMAIL PROTECTED], on 09/21/2005 at 10:34 AM, McKown, John [EMAIL PROTECTED] said: Thanks for the pointer. The explanation is fairly high level, with no implementation details. However, it appears that in the past (pre-z/OS 1.3), the page data sets were simply initialized by filling them with 4K blocks containing all binary zeros (or perhaps even random data?). That and creating BCS and VVDS entries. -- Shmuel (Seymour J.) Metz, SysProg and JOAT ISO position; see http://patriot.net/~shmuel/resume/brief.html We don't care. We don't have to care, we're Congress. (S877: The Shut up and Eat Your spam act of 2003) -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Curiousity: format of an unused page dataset?
-Original Message- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Glenn Miller Sent: Tuesday, September 20, 2005 9:01 PM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Curiousity: format of an unused page dataset? John, Take a look at APAR OW55297 on IBMLINK. It has a high-level description of what you're seeing on the Page Datasets. It also has references to other manuals. Glenn, Thanks for the pointer. The explanation is fairly high level, with no implementation details. However, it appears that in the past (pre-z/OS 1.3), the page data sets were simply initialized by filling them with 4K blocks containing all binary zeros (or perhaps even random data?). If this is so, then it would be relatively simple to initialize a page dataset that had somehow gotten defined, but not initialized properly. Muchas gracias! -- John McKown Senior Systems Programmer UICI Insurance Center Information Technology This message (including any attachments) contains confidential information intended for a specific individual and purpose, and its' content is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this transmission, or taking any action based on it, is strictly prohibited. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Curiousity: format of an unused page dataset?
OK, I'll admit that I'm sort of goofing off on this one. I was curious about the initial format of a never used page dataset. It appears to be quite simple except for one thing. What I have determined is: 1) The entire dataset is formatted into 4K physical block. This makes sense. 2) Every block on the first track is identical and contains: C9D3D9D7 C1C7C4E2 0100 BDA44D94 9A07ED00 *ILRPAGDS.u(m* 3) The 8 bytes at offset 16 vary, but not depending on the size of the dataset. 4) Every block on every track after the first track is identical and is binary zeros. The question is about point 3. Does anybody know what that value is? My best guess is that it is the output from an STCK. If so, does anybody know what it is used for by ASM? I have noticed that it changes while the dataset is active. Once the dataset is in use, it appears that all blocks are used for page frames, except the first block. This appears to have information in it such as the CPUID, the SYSNAME, the LPARNAME, another two timestamps (at +24 and +32), and maybe more that is not blindingly obvious. My initial curiousity about this was due to an old problem about defining a page dataset in an alternate catalog where the HLQ of the new page dataset was not in the standard catalog search order. As we all know, this results in the page dataset not be usable. So, in my idiocy, I thought this would be a neat function in ZZSA. The ability to format a page dataset from a stand alone utility. Granted, most people would just do things the right way. But what about the possibility of a FlexES user who has goofed up and no longer has an IPLable system due to this problem. Oh well, just shooting the bull, I guess. -- John McKown Senior Systems Programmer UICI Insurance Center Information Technology This message (including any attachments) contains confidential information intended for a specific individual and purpose, and its' content is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this transmission, or taking any action based on it, is strictly prohibited. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Curiousity: format of an unused page dataset?
It's even sillier on VM. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Curiousity: format of an unused page dataset?
John, I think you have it correct. The second block has a timestamp. I wrote a program to read the first record of the PLPA and had to change it to read the second page (see below) to report on the creation date/time of the PLPA. Used it to verify a CLPA really got done at IPL time. The first block data is correct. It was introduced recently (5 years?) to prevent simultaneous sharing of page datasets by different lpars. We did that for a week - lots of unexplained outages till we noticed. Alan -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Curiousity: format of an unused page dataset?
John, Take a look at APAR OW55297 on IBMLINK. It has a high-level description of what you're seeing on the Page Datasets. It also has references to other manuals. I printed the 1st block for a couple of my Page Datasets ( they were formatted by a z/OS R4 system and are being used by active z/OS R4 systems ) and the information seems to match what you identified. Based on my systems, the 3 STCK values seem to represent: +16 = TOD Clock when the Define Pagespace command was executed ( not sure if its started or ended ). +24 = TOD Clock when the Pagespace was accessed ( maybe when ASM was initialized at IPL time? ). +32 = TOD Clock when the 'status update' was performed The timestamp at +24 looks odd to me because all my Page Datasets for any one z/OS image have the same value. The timestamp seems to be within a .1 seconds of the message you get at IPL: IEA940I THE FOLLOWING PAGE DATA SETS ARE IN USE: PLPA ... - HLQ1.PLPA COMMON . - HLQ1.COMMON LOCAL .. - HLQ1.LOCAL The timestamp at +32 appears to change every 5 minutes on one of my sandbox z/OS R4 systems. I haven't had time to check another system that would be more active than my sandbox system. HTH Glenn Miller --- This message (including any attachments) is confidential and may be privileged. If you have received it by mistake please notify the sender by return e-mail and delete this message from your system. Any unauthorised use or dissemination of this message in whole or in part is strictly prohibited. Please note that e-mails are susceptible to change. ABN AMRO Bank N.V. (including its group companies) shall not be liable for the improper or incomplete transmission of the information contained in this communication nor for any delay in its receipt or damage to your system. ABN AMRO Bank N.V. (or its group companies) does not guarantee that the integrity of this communication has been maintained nor that this communication is free of viruses, interceptions or interference. --- -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
