z/OS V1.7: Expanding The Limits

sunfloweremryologistData Management

Oct 31, 2013 (3 years and 9 months ago)

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1



z/OS V1.7: Expanding The Limits




A hallmark of many recent IBM mainframe software announcements has been the expansion of logical limits,
hardware exploitation, and increasing the scale of applications that can efficaciousl
y be executed. zArchitecture
expanded the addressing capabilities of z/OS from gigabytes to exobytes. The number of LPARs in a physical
processor has continually grown, the number and bandwidth of channels has exploded, storage in cache
controllers now
rivals or exceeds that of main processors, and overall I/O throughput of a FICON storage
subsystem moves at dizzying speeds. z/OS has supported these new capabilities as they have emerged, and IBM
subsystems (CICS, DB2, IMS, Websphere, etc.) have evolved
to exploit these capabilities. The subsystems
themselves have also eased restrictions of internal limits. Perhaps no version of subsystem software has so
drastically expanded logical constraints in almost every corner of the product as DB2 Version 8 has;

CICS TS
Version 3 has among other things removed the 32K COMMAREA restriction and provided 64
-
bit addressing
toleration. As business and information system demands have grown, so have the capabilities of the software that
manages and enables these applic
ations. z/OS V1.7 continues this trend with robustness. Here’s a look at the
facilities provided in z/OS V1.7 that expand the limits of the zSeries


and its successor, the z9


environment.


Expanded LPAR Support.


z/OS V1.6 as originally delivered supp
orted between 1 and 24 processors in a single logical partition on z990
servers. z/OS V1.7 extends that support up to 32 processors that can be assigned to a single LPAR on a z990 or
z9 processor with good scalability characteristics (based on internal IB
M testing and measurements). This
support has been retrofitted to z/OS V1.6.

However, if zAAP processors (used for specialized Java processing) are being used in an LPAR, these processors
take the place of general
-
purpose processors, and thus reduce the t
otal number of general
-
purpose processors
available in a specific logical partition.

In addition, it is now possible to define up to a maximum of 60 logical partitions on a single z9
-
109 processor,
and to define up to 15 LPARs for a given Logical Channel S
ubsystem. This is not due to z/OS V1.7
enhancements, but rather to the hardware, microcode, and other components available in the z9
-
109.


Multiple Subchannel Set Support.


One of the new features of the z9
-
109 is multiple subchannel set support. z/OS V1
.7 exploits this feature by
enabling the use of a second subchannel set. As the number of DASD volumes has increased in large z/OS
installations, the existing limit of 64K unit control blocks (UCBs) has posed more and more challenges to more
and more z/OS

systems. By providing the ability of using a second subchannel set, z/OS has doubled the number
of UCBs


or logical DASD and tape devices


that can be used. Specifically, the second subchannel set can be
used for defining Parallel Access Volume (PAV)
aliases. Thus all addresses on the first subchannel set can be
used for real devices. EREP support for the second subchannel set is included.

In this z9 scenario, subchannel set 0 provides 63.75K subchannels, and subchannel set 1 provides 64K minus 1
sub
channels. Note that on zSeries and earlier machines, only 63K subchannels are available on set 0: 1,024
subchannels are reserved, so it is only possible to define and use 64,512 (63K) UCBs. The z9
-
109 only reserves
256 subchannels, freeing an additional
768 subchannels on subchannel set 0 for productive use. 768 3390
-
sized
volumes equals an additional 41 terrabytes of DASD storage. So the z9
-
109 running z/OS V1.7 increases the
number of real devices that can be used on the first subchannel set in additi
on to providing the second subchannel
set for PAV aliases. See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/CBDZUG40/2.1.2

for more
details.

Lastly, Workload Mana
ger (WLM) supports multiple subchannel sets in z/OS V1.7.


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Expanded VSAM and Data Set Limits.


z/OS V1.7 alleviates VSAM and general data set restrictions, and expands capabilities by providing significant
extensions in various ways. Sizes are enlarged, c
ounts are increased, logical restrictions are eased in the case of
many different facilities. Here’s a quick list of the most significant enhancements:


VSAM RLS 64
-
bit support.
VSAM Resource Level Sharing (RLS) under z/OS V1.7 has been enhanced to
enab
le the use of 64
-
bit storage for index and data buffers. Prior to this enhancement, buffers had to use 31
-
bit
storage and resided beneath the 2
-
gigabyte bar. This enhancement parallels DB2 V8’s new 64
-
bit buffering.
With the greater amounts of real memo
ry available on the zSeries and z9 processors, increasing buffers can very
positively impact I/O performance. To use 64
-
bit storage, the data set must in a data class defined as RLS Above
The 2
-
GB Bar, and PARMLIB member IGDSMSxx must specify RlsAboveTheB
arMaxPoolsize between 500
megabytes and 2 terabytes. See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/DGT2D440/2.9.2.4

for more details.


Expansion of VSAM exte
nt specification.

The previous limit of 255 extents for a VSAM data set component or
stripe has been removed in z/OS V1.7. This enhancement applies to both striped and non
-
striped data sets, and to
SMS data sets. This enhancement applies only to SMS
-
man
aged volumes. See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/DGT2D440/1.3.4

for more details.


Large
-
format sequential data set support.

z/OS had previously su
pported a data set size of greater than 64K
tracks for extended
-
format data sets. In z/OS V1.7, this support has been enhanced to include nonextended
-
format sequential data sets, assuming those data sets are accessed using QSAM, BSAM, or EXCP access
metho
ds. This can reduce the need for multiple
-
volume data sets. Unlike extended
-
format data sets, large format
data sets do not need to be SMS managed. This support is implemented via a new DSNTYPE=LARGE
specification on a DD statement, data class, or dynam
ic allocation equivalent. Certain restrictions apply unless
the BLOCKTOKENSIZE=LARGE is specified on the DCBE macro.

Not only has support for large format data sets been provided in z/OS V1.7, but a wide variety of z/OS facilities
already exploit this fea
ture under z/OS V1.7. Included in the list of products/elements that support this feature are
ISPF, SADMP, IPCS, AMASPZAP, DFSORT, DFSMSdss, and JES2/JES3 (for the spool).

In
addition, both
JES2 and JES3 have announced their intent to support a new maxim
um volume size for spool data sets. The
intended new maximum size will be implemented via the LARGE operand on the DSNTYPE parameter of the
DD statement for the spool, allowing the use of spool data sets up to 65,520 cylinders. Lastly, DFSMShsm and
DFSMS
rmm now support journal data sets of up to 16,777,215 tracks, reducing the number of CDS backups that
are required. Large format data set support is also provided for journal backup and certain temporary data sets.
See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/DGT2D440/3.6.11

for more details.


IODF Version 5.
Due to a generally expanding need for input and output device definitions in a large zSystem
install
ation, as well as new facilities such as multiple subchannel sets, Parallel Access Volumes, and Virtual Tape
Subsystems, the current limitation of 2 Gigabytes for an Input Output Definition File (IODF) is being approached.
IODF Version 5 has been re
-
archi
tected to eliminate the use of individual device definitions and to instead use
device groups,. IODF V5 implements a new format for device definitions, using device groups where devices
share common traits or characteristics such as device type, control u
nit attachment, processor(s)/channel
subsystems attachment, operating system, and esoterics. Device numbers must be in consecutive sequence. This
new format can dramatically reduce the size requirements of an IODF, and expand the number of devices in an
IODF. See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/CBDZUG40/2.1.5

for more details.


Other expanded/enhanced data set facilities.



The limit of DASD
-
only logst
reams on a single system has been raised to 16,384. The current limit is 1,024.



The Program Management Binder can now optionally compress program objects contained in PDSEs and
such UNIX System Services facilities as the zFS and HFS file systems.



Buffers
used by the SMF dump program (IFASMFDP) can now be placed above the 16M (that’s right, 16M,
not 2G) line.


3



The DFSMShsm Tape Table Of Contents (TTOC) has been expanded to provide enough records to allow the
definition and use of over 330,000 data sets per v
olume. An additional benefit of this enhancement is that it
allows for over 1,000,000 data sets per backup or migration tape volume, which new high capacity tape
cartridges are capable of



z/OS Storage Management is enhanced to conserve real storage below
the 16M line, and paging operations
during periods of heavy paging are more efficient.



Standalone dump I/O buffering is more efficacious, improving the performance of dumping storage and
prioritizing what data is dumped.



GTF and CTRACE now support VSAM lin
ear data sets, exploiting the performance capabilities inherent in
this data set type.



The summary dump size has been increased, which enhances first
-
failure data capture by improving the
possibilities of capturing necessary problem resolution data without

incurring the performance burden of
making a system nondispatchable while a dump is taken.


Hipersockets Support for IPv6.


Hipersockets provides a high performance, high thoughput facility within the Communications Server element of
z/OS for TCP/IP proce
ssing. IPv6 expands IP addressing capabilities by using 128 bits (rather than 32 bits) for
addressing objects within a TCP/IP network. This exponentially increases the number of devices or applications
that can be addressed, enabling the proliferation of

new TCP/IP users and devices such as cell phones and PDAs.
z/OS V1.7 combines these 2 facilities to provide powerful new options for mainframe systems. Hipersockets
support for IPv6 enables enhanced stack
-
to
-
stack communication between z/OS or LINUX sta
cks. It expands
connectivity alternatives between TCP/IP stacks in a sysplex. Implementing 128
-
bit addressing within the IP
address space provides full compatibility to an IPv6 Hipersockets environment. This support requires the use of a
z9
-
109 processo
r. See
http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/F1A1F210/HDRIPSHSO7

for
more details.


Where Can I Learn More?


Here are some references


and hyperlinks

to access them via the Internet


which discuss the topics reviewed in
this article in more detail. The bookshelves listed provide hyperlinks to all the unlicensed online manuals that are
part of the library for that product.



Title


URL

IBM Announceme
nt
-

Preview: IBM z/OS V1.7
& z/OS.e V1.7: World Class Computing

205
-
034

http://www.ibm.com/isource/cgi
-
bin/goto?it=usa_annred&on=205
-
034

IBM Announcement
-

IBM z/OS V1.7 deli
vers
advances in business resiliency & security

205
-
167

http://www.ibm.com/isource/cgi
-
bin/goto?it=usa_annred&on=205
-
167

z/OS V1R7.0 Introduction and Release Guide

GA22
-
7502

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/BOOKS/e0z2a161

z/OS V1R7.0 Overview Bookshelf

GA22
-
7497

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/e0z2bk60

z/OS V1R7.0 Planning & Installation Bookshelf

SA22
-
7830

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr
/Shelves/e0z2in60

z/OS V1R7.0 MVS Bookshelf

GA22
-
7479

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/iea2bk60

z/OS V1R7.0 JES2 Bookshelf

GA22
-
7481

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/has2bk50

z/OS V1R7.0 JES3 Bookshelf

GA22
-
7483

http://publ
ibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/iat2bk50

z/OS V1R7.0 DFSMS Bookshelf

GC35
-
0429

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/dgt2bk50

z/OS V1R7.0 Co
mm. Server Bookshelf

GC31
-
8792

http://publibfp.boulder.ibm.com/cgi
-
bin/bookmgr/Shelves/f1a1bk60

z/OS Home Page


http://www.ibm.com/servers/eserver/zseries/zos

z/OS Installation Home Page


http://www.ibm.com/servers/eserver/zseries/zos/installation

What’s New In z/OS?

SHARE

http://shareew.prod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S2838JE.PDF

MVS SCP Proceedings

SHARE

http://shareew.prod.web.sba.com/proceedingmod/project.cfm?Project_
ID=1714


4

Introducing the IBM System z9 109: Processor,
Memory and System Structure

SHARE

http://shareew.prod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S2849HE.pdf

Systems Center Hardware Update

SHARE

http://shareew.prod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S2830HE.pdf

Introducing the New Sequential Data Set

SHARE

Http://shareew.prod.web.sba.com/client_files/callpapers/attach/SHAR
E_in_Boston/S3025WRA.PDF

What's New in DFSMShsm


SHARE

http://sh
areew.prod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S3030eab.pdf

DFSMSrmm Boldly Goes Aboard the Enterprise

SHARE

http://shareew.pr
od.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S3041mw.pdf

VSAM Record Level Sharing (RLS) Overview

SHARE

http://shareew.prod.web.sba
.com/client_files/callpapers/attach/SHARE
_in_Boston/S3063tma.pdf

VSAM Record Level Sharing (RLS) 64
-
Bit
Buffering Enhancement

SHARE

http://shareew.p
rod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/S3065tma.pdf

MVS Storage Management Proceedings

SHARE

http://shareew.prod.web.sba.com/proceedingmod/pro
ject.cfm?Project_
ID=1715

JES2 for z/OS 1.7 Large Spool, NJE over TCP/IP,
and Other Features That Did Not Make the
Announcement Letters

SHARE

http://s
hareew.prod.web.sba.com/client_files/callpapers/attach/SHARE
_in_Boston/ACF3298.pdf

z/OS V1R7 JES3 New Features

SHARE

http://shareew.prod.web.sba.com/
client_files/callpapers/attach/SHARE
_in_Boston/s2721pk.pdf

What's New in z/OS Communications Server?

SHARE

http://shareew.prod.web.sba.com/
client_files/callpapers/attach/SHARE
_in_Boston/S3601_Whats_New.pdf


Product Availability, Service, and Compatibility.


While the focus of this article is z/OS V1.7 scalability, there’s another important reason to migrate to Release 7.
Many installations

still run z/OS V1.4, the last “staging” release that IBM has issued. A staging release is a
stable, extended
-
support release for customers who do not wish to regularly migrate to new releases. But it’s time
to seriously consider an upgrade. z/OS V1.7 i
s the last release to provide coexistence
\
fallback
\
migration
compatibility with z/OS V1.4. z/OS V1.7 will be supported until 09/2008 (projected), while z/OS V1.4 is
supported only until 3/31/2007. Thus, z/OS V1.7 provides 1½ additional years of support.

Lastly, it will not be
possible to order z/OS V1.7 after September, 2006. z/OS merits serious consideration for implementation. See
http://www.ibm.com/servers/eserve
r/zseries/zos/support/zos_eos_dates.html

for more details.