Modified Link Pack Area (MLPA) considerations
Posted by Rui Miguel Feio in MVS, Tech - Mainframe on September 4th, 2010
- It’s defined in SYS1.PARMLIB(IEALPAxx).
- Can be used to contain reenterable load modules from APF-Authorized libraries that are to be part of the pageable extension to the Link Pack Area (LPA) during the current IPL.
- Can only have PDS files. PDS/Es are not allowed.
- LPA modules that have been replaced through IEALPAxx are not physically removed from the PLPA or from the PLPA directory. They are however, logically replaced, because when one of them is requested, MLPA is searched first and then the system does not examine the LPA directory that contains the name of the replaced module.
- The system searches FLPA before MLPA for a particular module and selects the module from MLPA only if the module is not also in the FLPA.
- You may use IEALPAxx to temporarily add or replace SVC or ERP routines. Another possible application would be the testing of replacement LPA modules that have been altered by PTFs.
- Modules with an RMODE of 24 are placed in the MLPA, while those with an RMODE of ANY are placed in the extended MLPA.
Fixed Link Pack Area (FLPA) considerations
Posted by Rui Miguel Feio in MVS, Tech - Mainframe on September 4th, 2010
- It’s defined in SYS1.PARMLIB(IEAFIXxx).
- It’s a non-pageale area of storage.
- It’s loaded at IPL time from IEAFIXxx.
- The data sets in its concatenation must be in the Master Catalog.
- The Load modules must be kept in Fixed Storage Frames, ie, they cannot be paged out.
- This area should be used only for Load modules that should not allow page faults because of integrity considerations.
- Modules must be reenterant and refreshable.
- The advantage of using the FLPA is the reduction in the Central Storage available for paging old jobs and starting new jobs.
- Any library that includes modules for the FLPA must be a PDS. We cannot use PDS/Es in the LPALST concatenation.
- Because Fixed modules are not paged, we can save I/O time and paging overhead by placing moderately used modules into FLPA.
- The price for this performance improvement is the reduction in Storage available for paging old jobs and starting new jobs.
- Modules with an RMODE of 24 are placed in the FLPA, while those with an RMODE of ANY are placed in the extended FLPA.
Content:
- Load modules from LPALST concatenation, the LNKLST concatenation, SYS1.MIGLIB, and SYS1.SVCLIB can be included in the FLPA.
Notes:
- Pages referenced frequently tend to remain in Central Storage even if they are not Fixed.
Pageable Link Pack Area (PLPA) considerations
Posted by Rui Miguel Feio in MVS, Tech - Mainframe on September 4th, 2010
- It’s defined in SYS1.PARMLIB(LPALSTxx).
- It’s an area of Common Storage that is loaded at IPL time.
- This area contains SVC routines, access methods, and other READ-ONLY System Programs, along with any READ-ONLY reenterable user programs selected by an installation that can be shared among users of the system.
- There cannot be PDS/E data sets in the LPALST concatenation.
- Modules must be reenterant and executable.
- Programs in the PLPA are shared among users of the system.
- It is desirable to place all frequently used refreshable SYS1.LINKLIB and SYS1.CMDLIB modules in the PLPA.
- ASM maintains records that have pointers to the PLPA and Extended PLPA pages in the PLPA data set.
- During quick-start or warm-start IPLs, the system uses the pointers to locate the PLPA and Extended PLPA pages. The system then rebuilds the PLPA and Extended PLPA page tables, and uses them for the current IPL.
- If CLPA is specified during the IPL, a Cold start is then performed. The PLPA storage is deleted and made available for system paging use. A new PLPA and Extended PLPA are then loaded, and pointers to the PLPA and Extended PLPA pages are recorded in the PLPA page data set.
- The LPALST concatenation can have up to 255 extents. If you specify more data sets than the concatenation can contain, the system truncates the LPALST concatenation and issues messages that indicate which data sets were not included in the concatenation.
Contents:
- PLPA and Extended PLPA contain all the members of SYS1.LPALIB and any other libraries that are specified in the active LPALSTxx.
- The modules must be refreshable.
- Load modules with RMODE 24 are placed in the PLPA (below the “line”), while those with RMODE of any are placed in the Extended PLPA (above the “line”).
- If one or more LPALSTxx members exist, and the system can open the specified data sets successfully, the system uses the LPALST concatenation to build the PLPA (during Cold starts and IPLs that include the CLPA option). Otherwise the system builds the PLPA from only those modules named in the SYS1.LPALIB.
Link Pack Area (LPA) considerations
Posted by Rui Miguel Feio in MVS on September 4th, 2010
- It’s a common Virtual Storage Area.
- It’s non-getmainable.
- It’s built at IPL time by loading Load modules contained in SYS1.LPALIB and its concatenations.
- There are 2 LPAs: one above “the line” (16MB) and the other below depending on the residence mode of the load module.
- Because the Load modules are in the Common Area they are shared by all address spaces in the system.
- Modules have to be re-entrant, ie, modules that can be executed concurrently by several tasks but which cannot be modified.
- Modules in LPA reside in Virtual Storage.
- By placing module data sets in LPA, you can obtain improved MVS system performance.
- LPA consists of:
“Pirate Latitudes” – Book Review
Posted by Rui Miguel Feio in Books on September 3rd, 2010
Author: Michael Crichton
I admit Michael Crichton is my favourite writer. It’s a shame that he has passed away. I simply love his books.
However, when “Pirate Latitudes” first came out I was not entirely convinced if this would be the type of book I would want to read. A book about pirates? Now come on, in the past few years we’ve been bombarded with Pirates. In nowadays, when you think of Pirates, you think of Pirates of the Caribbean with Captain Jack Sparrow, Captain Hector Barbossa, Will Turner and the rest of the gang.
Having this in mind I wasn’t sure if Michael Crichton would be able to bring something new to the subject and captivate my attention and most of all, my imagination!
Oh, I was wrong! I was so, so wrong! After reading “Pirates Latitude” when I now think of Pirates, I still think of Jack Sparrow, but I also think of Captain Hunter, Lazue, Sanson, the Moor…
“Pirates Latitude” is a fantastic book! Michael Crichton as always, is able to take your mind to the worlds he imagined, and this time, the world was swarming with pirates!
A must buy book! Definitely!
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Story
Pirate Latitudes takes the reader back to 1665, when Charles II’s Jamaican colony is under serious threat, besieged on every side by the voracious Spanish empire. At the centre of this troubled outpost is its crowded capital, Port Royal, a lively (if festering) hangout for criminal dregs, who inhabit its taverns and brothels. This is the time of the privateer, when (with tacit royal sanction), ship’s captains could make sorties against Spanish ships and outposts, plundering at will — just so long as the Governor and King Charles are taken care of. Michael Crichton’s protagonist in this colourful mix is Captain Charles Hunter, educated at Harvard and a man with keenly developed survival instincts. He is made aware a treasure galleon, which is at anchor in the heavily fortified Spanish island of Matanceros, and Hunter’s interest is piqued — not least because this means he will be able to take on Philip of Spain’s most ruthless enforcer, Cazalla. The stage is set for what will either be a glorious bit of naval smash-and-grab or that will end in the ignominious death of Charles Hunter and his motley crew.
Display all the Storage Groups
Posted by Rui Miguel Feio in Storage, Tech - Mainframe on September 3rd, 2010
To display all the Storage Groups of the currently active SMS configuration, we use the command:
D SMS,SG(ALL)
Example:
D SMS,SG(ALL)
IGD002I 15:24:57 DISPLAY SMS 749
STORGRP TYPE SYSTEM= 1
SGTSTVL POOL +
SGDB2VL POOL +
DUMMY DUMMY .
SGOVRFL POOL *
SGTAPE TAPE +
***************************** LEGEND *****************************
. THE STORAGE GROUP OR VOLUME IS NOT DEFINED TO THE SYSTEM
+ THE STORAGE GROUP OR VOLUME IS ENABLED
- THE STORAGE GROUP OR VOLUME IS DISABLED
* THE STORAGE GROUP OR VOLUME IS QUIESCED
D THE STORAGE GROUP OR VOLUME IS DISABLED FOR NEW ALLOCATIONS ONLY
Q THE STORAGE GROUP OR VOLUME IS QUIESCED FOR NEW ALLOCATIONS ONLY
> THE VOLSER IN UCB IS DIFFERENT FROM THE VOLSER IN CONFIGURATION
SYSTEM 1 = SYST
Display the status of a storage group
Posted by Rui Miguel Feio in Storage, Tech - Mainframe on September 2nd, 2010
If you come across the need to check the status of a storage group then you can use the MVS command:
D SMS,SG(storage_group)
For example:
storage group name: STGTSTVL
RESPONSE=SYST
IGD002I 15:17:43 DISPLAY SMS 939
STORGRP TYPE SYSTEM= 1
SGTSTVL POOL +
***************************** LEGEND *****************************
. THE STORAGE GROUP OR VOLUME IS NOT DEFINED TO THE SYSTEM
+ THE STORAGE GROUP OR VOLUME IS ENABLED
- THE STORAGE GROUP OR VOLUME IS DISABLED
* THE STORAGE GROUP OR VOLUME IS QUIESCED
D THE STORAGE GROUP OR VOLUME IS DISABLED FOR NEW ALLOCATIONS ONLY
Q THE STORAGE GROUP OR VOLUME IS QUIESCED FOR NEW ALLOCATIONS ONLY
> THE VOLSER IN UCB IS DIFFERENT FROM THE VOLSER IN CONFIGURATION
SYSTEM 1 = SYST
If you would like to list the volumes that are part of the Storage Group, you would then issue the command:
D SMS,SG(SGTSTVL),LISTVOL
IGD002I 15:20:50 DISPLAY SMS 737
STORGRP TYPE SYSTEM= 1
SGTSTVL POOL +
VOLUME UNIT SYSTEM= 1 STORGRP NAME
TST001 5B22 + SGTSTVL
TST002 5B23 + SGTSTVL
TST003 5B24 + SGTSTVL
***************************** LEGEND *****************************
. THE STORAGE GROUP OR VOLUME IS NOT DEFINED TO THE SYSTEM
+ THE STORAGE GROUP OR VOLUME IS ENABLED
- THE STORAGE GROUP OR VOLUME IS DISABLED
* THE STORAGE GROUP OR VOLUME IS QUIESCED
D THE STORAGE GROUP OR VOLUME IS DISABLED FOR NEW ALLOCATIONS ONLY
Q THE STORAGE GROUP OR VOLUME IS QUIESCED FOR NEW ALLOCATIONS ONLY
> THE VOLSER IN UCB IS DIFFERENT FROM THE VOLSER IN CONFIGURATION
SYSTEM 1 = SYST
Display system connectivity of the tape and optical libraries
Posted by Rui Miguel Feio in Storage, Tech - Mainframe on September 2nd, 2010
If you wish to display which libraries are connected to your system you can use the MVS command:
D SMS,LIB(ALL)
Example:
D SMS,LIB(ALL)
RESPONSE=SYST
IGD002I 15:10:50 DISPLAY SMS 869
LIBRARY CLASS SYSTEM= 1
TSTATL1 TAPE +
***************************** LEGEND *****************************
. THE LIBRARY IS NOT DEFINED TO THE SYSTEM
+ THE LIBRARY IS ONLINE
- THE LIBRARY IS OFFLINE
P THE LIBRARY IS PENDING OFFLINE
SYSTEM 1 = SYST
We can see in this example that we have a tape library online on system SYST called TSTATL1. If we wish to obtain more details regarding this library we issue the command:
D SMS,LIB(TSTATL1),DETAIL
CBR1110I OAM library status: 563
TAPE LIB DEVICE TOT ONL AVL TOTAL EMPTY SCRTCH ON OP
LIBRARY TYP TYPE DRV DRV DRV SLOTS SLOTS VOLS
TSTATL1 AL 3584-L22 16 4 4 1060 187 148 Y Y
----------------------------------------------------------------------
MEDIA SCRATCH SCRATCH SCRATCH
TYPE COUNT THRESHOLD CATEGORY
MEDIA5 148 50 0005
----------------------------------------------------------------------
LIBRARY ID: A0669
OPERATIONAL STATE: AUTOMATED
ERROR CATEGORY SCRATCH COUNT: 9
----------------------------------------------------------------------
Convenience I/O station installed.
Convenience I/O station in Input mode.
Convenience I/O station Empty.
Bulk input/output not configured.
How to check if a volume is SMS-managed
Posted by Rui Miguel Feio in Storage, Tech - Mainframe on September 2nd, 2010
One of the ways (and probably the easiest) to check if a volume is SMS-managed is by using the MVS command:
D SMS,VOL(volser)
Here’s an example:
volume: TST001
Command:
D SMS,VOL(TST001)
The result would be:
RESPONSE=SYST
IGD002I 09:52:24 DISPLAY SMS 382
VOLUME UNIT SYSTEM= 1 STORGRP NAME
TST001 5B22 + SGTSTVL
***************************** LEGEND *****************************
. THE STORAGE GROUP OR VOLUME IS NOT DEFINED TO THE SYSTEM
+ THE STORAGE GROUP OR VOLUME IS ENABLED
- THE STORAGE GROUP OR VOLUME IS DISABLED
* THE STORAGE GROUP OR VOLUME IS QUIESCED
D THE STORAGE GROUP OR VOLUME IS DISABLED FOR NEW ALLOCATIONS ONLY
Q THE STORAGE GROUP OR VOLUME IS QUIESCED FOR NEW ALLOCATIONS ONLY
> THE VOLSER IN UCB IS DIFFERENT FROM THE VOLSER IN CONFIGURATION
SYSTEM 1 = SYST
As we can see from the display, volume TST001 has the unit address 5B22 and is part of the Storage Group SGTSTVL, meaning it’s SMS managed.
PHP parameter session.gc_maxlifetime is lower that cookie validity configured in phpMyAdmin
Posted by Rui Miguel Feio in PhpMyAdmin, WAMP on December 5th, 2009
If you have installed a new MySQL version you may be getting the following warning message:
Your PHP parameter session.gc_maxlifetime is lower that cookie validity configured in phpMyAdmin, because of this, your login will expire sooner than configured in phpMyAdmin.
To solve this issue we first need to check what the session.gc_maxlifetime value is in php.ini and what the $cfg['LoginCookieValidity'] is in config.inc.php.
Example:
1. php.ini
session.gc_maxlifetime = 1440
2. config.inc.php
$cfg['LoginCookieValidity'] = 1800;
Now, we only need to make these two values the same. For the sake of this example, we will change the value of $cfg['LoginCookieValidity'] to 1440.
After saving the changes we need to restart the services to make them effective.
Notes:
1.The php.ini file can be found on the php folder.
2. The config.inc.php file can be found on the phpmyadmin folder.
If you’re interested in learning more about PhpMyAdmin then check out the book “Mastering PhpMydmin for Effective MySQL Management“.