IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 36

tion (DAT) capability, enabling CP to use virtual memory to create separate address spaces for each virtual ser ver. To do this, CP creates a set of tables that contain detailed information on the status of each the real-memory locations the virtual machine uses. The DAT hardware uses these tables to convert virtual-memory addresses to real-memory addresses. Because CP maintains the tables in its own address space, the virtual machines themselves can’t access the tables and therefore can’t access the memory that CP or another virtual machine uses. Methods of sharing memory in z/VM require additional authorization. The interpretive-execution facility takes DAT a step further by supporting address translation while in both levels of SIE. A virtual server running under z/VM constructs its addresstranslation tables as usual to isolate and contain the memory for it s ow n processes. The entire memor y of a virtual server—although the vir tual ser ver’s OS views it as real memory— is in fact virtual memory as well, def ined by another set of translation IBM has implemented specific tables CP manages. Even design and coding guidelines for if an application running maintaining system integrity in the in a virtual server were development of z/VM. Procedures able to compromise the have also been established to integrity of that server, make the application of these t he d a m a ge wou ld b e design and coding guidelines l i m i t e d t o t h a t o n e a formal part of the design and v ir t ual ser ver because development process. However, because it isn’t of the separate layer of protection provided by possible to certify any system S y s t e m z h a r d w a r e has perfect integrity, IBM will accept [problem reports] that and z/VM. At the discretion of the describe exposures to the z/V M system adminis- system integrity of z/VM or that trator, CP can exploit the describe problems encountered same mechanisms that when a program running in a pr ov ide s uc h me mor y virtual server not authorized by a i solat ion to sha re one mechanism under the customer’s or more memor y blocks control introduces an exposure among multiple virtual to the system integrity of z/VM… s e r v e r s . T h i s s h a r e d IBM will continue its efforts to memory helps the system enhance the integrity of z/VM and to respond promptly when exposures are identified. —A.A. While hardware support for virtualization now appears in both Intel and AMD processors, the System z solution is the only platform that has two levels of hardware virtualization. z/VM System Integrity Statement manage memory more efficiently by dramatically reducing the number of duplicate page frames. Shared memor y can be read-only or read-write blocks of memory containing code and/or data that many virtual servers can access. It’s valuable, for example, for several Linux* virtual servers to share application binaries in order to reduce the demand for real memory. This is an instance where the CP-managed DAT tables that describe various virtual servers will all point to the same page frames in real memory. z/VM uses additional hardware memory-protection mechanisms to ensure an unauthorized virtual server can’t alter shared, read-only memory. Virtual Devices CP erects a barrier between virtual servers and the devices to which CP has access. A primary function of CP is to mediate access to those real devices in different ways, depending on whether the device is intended to be shared between two or more virtual servers simultaneously, or whether the device is to be made available for the exclusive use of a single virtual server. When a virtual server makes an I/O request, CP intercepts the request and translates virtual-memory addresses in the I/O request to their corresponding real-memory addresses. In addition, CP examines the I/O request so no potentially harmful device-maintenance requests or device-subsystem functions are performed, unless the z/VM system administrator has granted special authorization. Once the I/O operation has been validated, CP performs the I/O operation on behalf of the virtual server. As with memory, DASD devices can be partitioned into multiple units called minidisks. Each minidisk appears as a separate disk volumes to the virtual servers. A minidisk can be as small as a single block or cylinder, or may cover an entire DASD volume. A reference by the virtual server to cylinder 0 might be mapped as, for example, cylinder 100 36 M AY/J U N E 2 0 0 8 ibms ystemsmag .com/mai nframe

IBM Systems Magazine, Mainframe digital edition - May/June 2009

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe digital edition - May/June 2009

IBM Systems Magazine, Mainframe digital edition - May/June 2009
Table of Contents
Editor's Desk:  High-Flying Security
Trends:  IBM Cognos 8 BI for Linux on System z Makes Reliable Data Available Anywhere
IT Today:  New System x and BladeCenter Servers Help Your Organization Reach Its Goals
Focus on Storage: Virtual Tape Facility for MainframeJoins IBM Arsenal
Q & A:  Hybrid Technology Takes Supercomputing Beyond Moore’s Law
Case Study:  The City and County of Honolulu Allows Its Applications to Dictate the Platforms on Which They Run
Cover Story:  IBM’s z/VM is a Proven Solution for Today’s IT Environments
Feature:  IBM’s Dynamic Infrastructure Helps Companies Reduce Costs, Manage Risks and Improve Services
Administrator:  DB2 9 Features Help Ensure Compliance
Product News
Advertiser Index
Stop Run:  Barry Merrill’s Accidental DiscoveriesEnhance the Mainframe
Reference Point
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - IBM Systems Magazine, Mainframe digital edition - May/June 2009
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover2
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 1
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Table of Contents
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 3
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 4
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 5
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 6
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 7
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Editor's Desk:  High-Flying Security
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 9
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Trends:  IBM Cognos 8 BI for Linux on System z Makes Reliable Data Available Anywhere
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 11
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 12
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 13
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - IT Today:  New System x and BladeCenter Servers Help Your Organization Reach Its Goals
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 15
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 16
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 17
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 18
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 19
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Focus on Storage: Virtual Tape Facility for MainframeJoins IBM Arsenal
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 21
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 22
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 23
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Q & A:  Hybrid Technology Takes Supercomputing Beyond Moore’s Law
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 25
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 26
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 27
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Case Study:  The City and County of Honolulu Allows Its Applications to Dictate the Platforms on Which They Run
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 29
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 30
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 31
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover Story:  IBM’s z/VM is a Proven Solution for Today’s IT Environments
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 33
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 34
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 35
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 36
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 37
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 38
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 39
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Feature:  IBM’s Dynamic Infrastructure Helps Companies Reduce Costs, Manage Risks and Improve Services
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 41
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 42
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 43
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 44
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 45
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 46
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 47
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Administrator:  DB2 9 Features Help Ensure Compliance
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 49
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 50
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 51
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Product News
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 53
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - 54
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Advertiser Index
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Stop Run:  Barry Merrill’s Accidental DiscoveriesEnhance the Mainframe
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover3
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Cover4
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - Reference Point
IBM Systems Magazine, Mainframe digital edition - May/June 2009 - RF2
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