HP 3000 Application Note

 Worldwide Response Center
HP 3000 APPLICATION NOTE #79
Conquest Of Disc Space
HEWLETT November 15, 1990
PACKARD Document P/N #5960-4625
"RESPONSE CENTER APPLICATION NOTES
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CONQUEST OF DISC SPACE
There is one notion that all people in charge of computer operations, no matter what the size, are far
with the notion of disc space.
For the most part, the correct operation of a system, its availability as well as its performance all de
on how well this space is used. We shall go into a certain number of notions within in the framewd
MPE XL.
As with any other operating system, MPE XL also manages disc space.
Under MPE V, two notions apply to disc management.
1. Part of the disc is reserved for virtual memory which can be seen as an extension of
memory.
2. The remainder of the disc is used for storing files.
Under MPE XL, equivalent notions are used. In this Application note we will describe them 1
theoretically and the practical aspects of their use. We shall address the different types of files tha!
be found under MPE XL, the domain in which they are installed and how they affect occupied disc sj
Presented next is a description of several utilities related to these notions. We shall compare the v:
niliar
spend
rk of
main
n the
| may
pace.
Arious
points covered concerning the notion of private volume and finally, we shall give some hints on how to
solve some of the most frequently encountered problems.
SOME NOTIONS:
-Disc space, permanent space, transient space.
A disk contains programs, databases, etc. There are also DIRECTORIES, files used by TRANSAC
MANAGEMENT, tables of FILE LABELS and EXTENT descriptors.
File labels (not to be confused with USER LABELS) and EXTENT descriptors are actually gr
together at the beginning of a volume and because of this are not contiguous with data in the file.
done mainly to simplify a certain number of maintenance operations such as RECOVER LOST
SPACE.
Finally, a small section of the disc contains areas reserved for the system. This makes up the
permanent space. The items which we have just mentioned are intended to remain for a long time «
disc. It is therefore essential to have a system to maintain these items. This maintenance is provided
DIRECTORY, just as they are handled under MPE У.
We shall not go into details on the internal structure of MPE XL DIRECTORY here, however rem
that this structure is different from the one used under MPE V.
TION
ouped
[his is
DISC
disc’s
bn the
1 by a
ember
When main memory is full, the system must be able to manage saturation and remove what is not used.
Under MPE V, virtual memory is used. This is a disc area configured only once.
Under MPE XL, there is no predefined system area. Instead. there is the notion of transient space.
Transient space is defined as the disc space occupied by data that the system had to remove from main
memory. Transient space is therefore a dynamic notion and not a fixed oñe as under MPE V. The pages
removed from the system’s main memory will be placed on the disc in free space and not in a predefined
area.
It is obvious that the sum of permanent space, transient space and free space must equal the total disc
space. -
-Disc space allocation:
As far as files are concerned there is no problem. They are always allocated to permanent space whether
they are permanent files, temporary files or NEW files.
The following objects are also allocated to permanent space: TRANSACTION MANAGEMENT files
(approximately 400,000 sectors per VOLUME SET), DIRECTORIES, tables of FILE LABELS and EXTENT
descriptors.
Transient space contains objects that the system has removed from main memory, in other words, basically
data areas, STACKS and other control blocks of the FILE SYSTEM or TurboIMAGE.
It is clear that the notion of transient space replaces that of virtual memory used under MPE V which was
very static. However, certain limits must nevertheless be set down so that the system will run
satisfactorily. This is why each volume is provided with a maximum percentage of transient space and a
maximum percentage of permanent space. “Do not forget that these percentages represent maximum
values, which means their sum total may be greater than 100% For example, default configurations
‘anticipate maximum values of 75% permanent. space and 75% transient space per configured volume. It is
obvious that both these maximum values cannot be reached simultaneously.
However, using dynamic . space allocation provides a certain amount of flexibility to disc space
management. Certain: activities are transient-space - intensive (system startup or certain applications
which handle large volumes of data) whereas, others require a large amount of permanent space in the
form of f iles. There are also some special cases.
We shall cover two of them.
l. The system considers SPOOL files as permanent objects and are therefore allocated to permanent disc
space just like any other file. They are installed on discs with SPOOL class whether these discs are system
or private domain volumes.
2. Private volumes are used exclusively in permanent space. The system never places transient objects in
them and this way does not know the maximum percentage configured for transient space.
With the basic notions defined, We shall now describe some very useful programs.
UTILITIES : VOLUTIL, DISCFREE, FSCHECK
We have touched on the maximum limit ín ‘terms of permanent and transient disc space which can be
- reached on a given volume. | | |
Only the values set using VOLUTIL are used. The ones included in SYSGEN are ignored by the system.
VOLUTIL
The commands NEWVOL and ALTERVOL are used, with their key words PERM- and TRANS-, to
define or change values. By default, in other words, 1f nothing is specified when using NEWVOL, the
system allocates a maximum of 75% to permanent space and 75% to transient space. Е |
Once again, the notion of disc size requirements is a dynamic one and in no way sets the physical |
allocation of space. For the exact syntax of these commands, refer to the MPE XL: VOLUME
MANAGEMENT manual, (Hewlett-Packard p/n 32650-90045). о |
It is important to know the actual space used, so that disc space can be correctly managed. The utility
which performs this is called DISCFREE which replaced FREES under MPE V. o |
DISCFREE
This program uses two parameters, A and B. DISCFREE A provides a sort of histogram, similar to the one
in FREES. DISCFREE B provides the total space, the permanent space, the transient space, the free space
and the maximum remaining space which can be allocated to permanent and transient space for each
volume. |
DISCFREE B
DISCFREE A. 00.04 Copyright (C) Hewlett-Packard 1988. All rights reserved.
ALL MEASUREMENTS ARE IN SECTORS.
== UN ES > ES ES ÓN GEL EN EE A A Wr ME GR AL E WS A EP EE A CD чи A ES O US O de E E E E
LDEV :: 1 -- (MPEXL SYSTEM VOLUME_SET:MEMBER1)
DEVICE SIZE : 1579904
TRANS SPACE 338896 | PERM SPACE : 1151888
MAX TRANS SPACE : 1184928 | MAX PERM SPACE : 1200720
FREE SPACE : 89120 |
AVAIL TO TRANS SPACE : 89120 - AVAIL TO. PERM SPACE : 4883?
DEVICE SIZE is the physical size of the disc. It is an HP7935 with 404 megabytes, therefore 1579904
sectors. nn | |
TRANS SPACE and PERM SPACE are the transient and permanent space occupied when the command
‘was initiated. | |
FREE SPACE is of course the volume's free available space.
AVAIL TO TRANS and AVAIL TO PERM are the transient and permanent space available depending on
the MAX TRANS SPACE and MAX PERM SPACE values which are the maximum values assigned under.
VOLUTIL (refer to VOLUTIL Section presented above). |
In the example shown, AVAIL TO PERM SPACE is less than FREE SPACE, because if we allocate the
89120 sectors (free space), which are physically available, to permanent space, we get a total of 1241008
sectors (Perm space + Free space) which is greater than the maximum configured value of 1200720 (Max
perm space).
The LDEV 1 system disc represents a special case. For all the other volumes we can define maximum
| values of 100% for both permanent and transient space. à -
For LDEV 1, however, we cannot define more than 76% for permanent space.
3
VOLUTIL accepts the value 77% but only takes 76% into account. The reason for this difference is that
in order to ensure system startup and correct operation in SINGLE DISC mode (if a single disc is available
at startup) or if only one disc is configured, a certain amount of transient space must be available.
- NOTE
Regardless of the type of stártup, this required transient space must not be
confused with the permanent and contiguous space which must be available
for startup from an UPDATE or UPDATE CONFIG tape.
FSCHECK
FSCHECK is another utility which may be very useful. The only usable version of FSCHECK is the one
installed in the PRVXL group in the TELESUP account which is recognized by its EOF at 810. Any other
version must not be used as it may be dangerous and should be purged.
The most frequently used command is SYNCACCOUNTING. This command has a single parameter,
which is a VOLUME SET name, and is used to update the disk space information provided by the
REPORT command to the actual situation. The reason for this is that when certain actions are taken,
such as a massive purge of IPC files, the information provided by REPORT may be wrong. For the system
domain, there is no need to specify a parameter since the MPE domain XL. SYSTEM_ VOLUME_ SET is
taken by default. a.
SOME USEFUL REMARKS
We have already mentioned the fact that a certain amount of disc space must be available for an
UPDATE or UPDATE CONFIG in order to install a PATCH or update the MPE XL. It is important to
keep this requirement and its’ required values in mind.
In all cases you must have §5,000 contiguous sectors in permanent space on the LDEV 1. Moreover, a
total permanent space of 500,000 sectors, not necessarily contiguous, is required for all the volumes of the
system domain in permanent space. By observing this simple rule, UPDATE or UPDATE CONFIG startups
can be done without the risk of having the procedure stopped by an "OUT OF DISC SPACE" error.
The following message may sometimes be displayed on the system console:
"WARNING - DISC SPACE IS LOW - ONLY JOBS/ SESSIONS WITH HIPRI MAY LOGON".
This message means that disc space has reached a low point and should not be decreased any more by
creating new objects. The answer is to restore free space by any means available, such as by deleting
certain sessions or jobs or by purging some permanent files.
You will note that the system reverts to normal operation when the console displays the follo
message:
"JOBS AND SESSIONS MAY LOGON NORMALLY".
wing
As you have seen, the use and management of disc space under MPE XL are governed by a few simple
rules: transient space and permanent space are two of the mainfacets.
We hope we have clarified a certain number cf simple, however essential ints so that your systems
run smoothly and users are fully satisfied.
Computer
Museum
will
Published Application Notes
HP 3000
Following i is a list of the Application Notes s published to date. If you would like to order single
copies of back issues please use the Request Form attached and indicate the number(s) of the
note(s) you need, and the part number(s).
Note # | Part Number Topic
1 5958-5824 Printer Configuration Guide - Version 1
2 5960-2841 | Terminal types for HP 3000 HPIB Computers - Version 1
3 5960-2842 | Plotter Configuration Guide
4 5960-2843 | Printer Configuration Guide - Version 2
5 5960-2844 | MPE System Logfile Record Formats
6 | 5960-2845 |Stack Operation В
7 5960-2846 |COBOL 11/3000 Programs: Tracing Illegal Data
—8 5960-2847 | KSAM Topics: COBOL's Index I/O: File Data Integrity
9 5960-2848 | Port Failures, Terminal Hangs, TERMDSM
10 5960-2849 - Serial Printers - - Configuration, Cabling, Muxes
11 5960-2850 System Configuration or System Table Related Errors
12 5960-2851 | Pascal 3000 - Using Dynamic Variables
13 5960-2852 | Terminal Types for HP 3000 HPIB Computers - Version 2
14 9960-2853 | Laser Printers - A Software and Hardware Overview
15 5960-2854 [FORTRAN Language Considerations - A Guide to Common Problems
16 | 5960-2855 |IMAGE: Updating to TurboIMAGE & Improving Database Loads
17 | 5960-2856 [Optimizing VPLUS Utilization
18 | 5960-2857 |The Case of the Suspect Track for 792X Disc Drives
19 5960-2858 | Stack Overflows: Causes & Cures for COBOL II Programs
20 | 5960-2859 |Output Spooling |
21 | 5960-2860 |COBOLII and MPE Intrinsics
22 | 5960-2861 | Asynchronous Modems
Published Application Notes 1!
HP 3000 (continued)
Note # | Part Number Topic
23 5960-2862 | VFC Files
24 5960-2863 | Private Volumes |
25 5960-2864 |TurboIMAGE: Transaction Logging
26 5960-2865 | HP 2680A, 2688A Error Trailers |
27 5960-2866 | HP Trend: An Installation and Problem Solving Guide
28 5960-2867 |The Startup State Configurator |
29 5960-2868 |A Programmer’s Guide to VPLUS 3000
30 | 5960-2869 |Disc Cache |
31 5960-2870 Calling the CREATEPROCESS Intrinsic
32 | 5960-2871 |Configuring Terminal Buffers
33 5960-2872 Printer Configuration Guide - Version 3 |
34A 5960-2873 |RIN Management (Using COBOLII Examples) (A)
34B 5960-2874 | Process Handling (Using COBOLII Examples) (В)
35 5060-2875 |HPDESK IV (Script files, FSC, and Installation Considerations)
34C 5960-2876 |Extra Data Segments (Using COBOLII Examples) (C)
36 5960-2877 | Tips for the DESK IV Administrators
37 5960-2878 | AUTOINST: Trouble-free Updates
38 5960-2879 |Store/Restore Errors
39 5960-2880 |MRJE Emulates a HASP Workstation
40 5960-2881 |HP 250 / 260 to HP 3000 Communications Guidelines
41 | 5960-2882 |MPE File Label Revealed
42 5960-2883 |System Interrupts
43 5960-2884 |Run Time Aborts
44 | 5960-2885 |HPPA Patching Conventions for HP3000 900 Series Processors - Version 1
45 5960-2886 | Vplus & Multiplexers
46 5960-2887 |Setting Up an HPDesk HPTelex for the First Time
47 5960-2900 | Customizing Database Data Items & Changing Passwords in JCL Files
48 5959-9215 | Printer Configuration - Version 4 |
49 5959-9227 | Configuring DATACOMM Products Into MPE
50 5959-9228 | VFC's for Serial Printers
| 2 Published Application Notes
| “HP 3000 (continued)
Note | Part Number — Topic
# a
51 | 5959-9237 | Terminal Types for the HP 3000 HPIB Computers
52 | 5959-9242 |Configuring MRJE
53 5959-9245 | Using Special Characters on the 700/9x Series Terminals
54 | 5959-9251 (Improving Database Performance
55 5959-9258 | Customized Message Catalogs and Help Facilities
56 | 5059-9266 |BRW Tips for Beginners
57 | 5959-9270 Configuring the HP 2334A Plus & HP 2335A As a Statistical Multiplexer
58 5959-9274 | HPPA Pathing Conventions for HP3000 900 Series Processors - Version 2
59 5959-9289 | HP 2334A and HP 2334A Configuration Recipes
60 5059-9301 | TurboIMAGE'’s I-FILES and J-FILES
61 5959-7385 HPDeskManager - Looking Behind the Scenes
62 5959-7803 [Setting Up a System Dictionary |
63 | 5959-7834 |Configuring Telesupport Modems for MPE V/E Systems
64 5960-1816 | Finding Solutions | in HP SupportLine |
65 | 5960-1817 | Using the Electronic Call Feature of HP SupportLine
66 | 5960-1818 | Using the Feedback Feature of HP SupportLine
67 5960-1819 | Printing Documents from HP SupportLine
68 5960-1820 |HP SupportLine Commands
69 5960-2901 | Nonsystem Volume Sets and the Migration of Private Volumes to an
$9000 HP 3000
70 5960-2907 | Modem Links for Remote Console and Standard DTC Connections on
Commercial XL. HPPA Systems
71 5960-2918 | Asynchronous Cabling
72 5960-2919 | BRW Tips and Tricks
73 5960-2998 |SNA NRJE Configuration
74 5960-2999 |SNA IMF Configuration
75 5060-3000 |XL NRJE Configuration
76 5960-4301 | XL IMF Configuration
77 | 5960-4302 |Calling the BRW Intrinsics
78 | 5960-4303 |PUB.SYS What Is Behind It?
79 | 5960-4625
Conquest of Disc Space
Published Application Notes 3
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