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Directory Processing for Multiconfiguration Virtual Machines with Object Directory Compatibility during Migration

IP.com Disclosure Number: IPCOM000199674D
Publication Date: 2010-Sep-14
Document File: 2 page(s) / 43K

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A source user directory is a file consisting of statements that define the configuration and operating characteristics of each virtual machine that can be created on a z/VM system. This source file is converted into an object directory that z/VM uses to create a virtual server (herein called a virtual machine) when a user is logged on. DIRECTXA is a program provided with the z/VM operating system to convert a source user directory file into an object directory. With the creation of the Single System Image (SSI) cluster environment in the z/VM operating system, there came a need to define a virtual machine that could have different directory settings on each system in the SSI cluster. This new Multiconfiguration virtual machine can be logged on to more than one system in the SSI cluster at the same time. The directory entries for this virtual machine will consist of definitions that are common to all systems in the SSI cluster and definitions that are unique to each system in the SSI cluster. The identity and authorizations of the virtual machine will be the same no matter what system it is logged on to. However, resources can be defined to be either common to all instances of the multiconfiguration virtual machine throughout the cluster, or unique to a specific instance on one system in the cluster. An example of this would be disk definitions. Some disks will be shared among all the systems in the cluster and must be defined to allow for this sharing. Other disks will be local to one system in the cluster. These disks must be defined so that they are kept private to one system and not shared among all the systems. Each multiconfiguration virtual machine instance would get its own unique disk area defined as private. Our goal was to change DIRECTXA to provide this support while also satisfying the following requirements: DIRECTXA must produce an object directory that can be used by any system in the SSI cluster. This means that all system-specific information for all systems in the SSI Cluster must be maintained in the object directory. A migration path must be provided to evolve an existing single z/VM system into a cluster of systems. This migration path must allow an object directory created by DIRECTXA for the current stage of migration to be used if a customer needs to back off to the preceding stage in the migration path. The DIRECTXA utility in z/VM already had support for CSE Cluster systems. This support allowed statements in the user directory to be included or excluded based on which system the directory was being built for. The drawback to this solution was that the object directory created from running DIRECTXA could only be used with the one specific system that was determined at the time DIRECTXA was run. Any virtual machine settings that existed in the source directory for other systems in the CSE complex were nonexistent in the object directory that was created by DIRECTXA. Our goal was to have DIRECTXA produce an object directory that could be shared among all of the systems in the SSI Cluster. The DIRECTXA utility has always maintained object directory compatibility. The need to maintain directory settings for all systems in a single object directory caused significant changes to the object directory format. As a result, careful consideration was given to providing a migration path that allows a customer to use the same object directory with two consecutive stages in the migration path.

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Directory Processing for Multiconfiguration Virtual Machines with Object Directory Compatibility during Migration

In previous implementations of DIRECTXA, all directory settings for a virtual machine were merged into a single virtual machine definition block in the object directory. If a source directory had system-specific settings, only the settings specific to one system would be included in the virtual machine definition block. Therefore, a separate object directory needed to be created for each system that was using the shared source directory.

     This invention can be implemented by creating multiple virtual machine definition blocks in the object directory for a multiconfiguration virtual machine. New statements can be used in the source directory to indicate that a multiconfiguration virtual machine is to be defined. One virtual machine definition block is created for all of the common virtual machine settings. Additional virtual machine definition blocks are then created for each set of system-specific definitions. When a virtual machine is logged on to a system in an SSI cluster, a lookup is done to find the virtual machine definition block for the userid and then a second lookup is done to determine if there is an additional virtual machine definition block with system-specific settings that need to be merged at logon time.

     This invention also calls for a method to create two different formats of object directories. One format has a single virtual machine definition block for each virtual machine in the source directory. Merging system-specific definitions with the common virtual machine definitions at directory-creation time allows for the creation of an object directory that can be used by a non-SSI or single-member SSI system, as well as by an earlier release of z/VM that does...