Understanding your system resources is a necessary part of troubleshooting. Resources include memory, mass storage, network access, processor power, and so on. When your program needs a hardware resource, it makes a request to the operating system. Windows then tries to fulfill the request and provide the software that the resources requested. If it doesn’t, you’ll find using your computer difficult to operate.
Operating Systems: A Modern Perspective, Chapter 10. Serially reusable resources: A unit must be allocated before being released; Consumable resources:.
Every time the PC starts, it takes inventory of its hardware. The operating system knows this information — not only when the computer starts but also as you add or remove components. You can see that information for yourself by using the System Information tool.
To start the System Information tool, from the Start menu choose All Programs→Accessories→System Tools→System Information. The System Information window opens. You see a quick summary of nerdy details about your computer, such as the type of processor installed, total memory, Windows version, and other technical tidbits.
To see specific information, choose a category from the left side of the window. The information is detailed and, by itself, useless. But when you need that specific information, you know where to find it.
The information shown by the System Information tool is static — it’s just a report. For more dynamic information, you use one of the Windows resource monitors.
- The final entry in the System Information window, beneath the heading Software Environment, is Windows Error Reporting. It’s a quick way to review recent mishaps in your computer.
- You can also type a command at the command prompt to get system information. The command is systeminfo, though if you want to use it, follow systeminfo with the pipe (|) character and then the word more, like this:This command provides a page of information to your screen at a time instead of just scrolling it endlessly.
Global Resource Serialization (GRS) is the component within the IBMz/OS operating system responsible for enabling fair access to serially reusable computing resources, such as datasets and tape drives or virtual resources, such as lists, queues, and control blocks. Programs can request exclusive access to a resource (which means that program and all subsequent requesting programs are blocked until that program is given access to the resource), usually requested when a program needs to update the resource or shared access (which means that multiple programs can be given access to the resource), usually requested when a program only needs to query the state of the resource. GRS manages all requests in FIFO (first in/first out) order.[1]
Scoping[edit]
GRS manages resources at three different levels of scoping:
- STEP - this level is for resources that exist within a single MVS address space. Only threads (tasks) within that address space can request access to the resource.
- SYSTEM - this level is for resources that exist within a single MVS instance. Any thread running on the system can request access to the resource.
- SYSTEMS - also known as GLOBAL, these resources are accessible by multiple MVS instances. Any thread running on a system in the GRS complex can request access to the resource.
Clustering[edit]
In order for GRS to serialize resources between multiple systems, the systems must be clustered. There are several options to enable this clustering:
- GRS Ring - each of the systems (LPARs) are connected with channel-to-channel adapters (CTCAs) in a ring configuration. The GRS software sends messages around the ring to ensure the integrity of the complex and to arbitrate correct succession of ownership.
- Basic Sysplex - each of the systems in the sysplex has complete connectivity to every other system via CTCAs or ESCON CTCAs, managed by the XCF (Cross System Coupling Facility) component. The GRS component utilizes the Messaging and Group Services provided by XCF to replace and augment the function through the GRS managed CTCAs.
- GRS Star (Parallel Sysplex) - Rather than using a message passing protocol to manage resource ownership succession, GRS uses the locking services provided by the XES (Cross System Extended Services) component of MVS. Use of locking services requires a lock structure (called ISGLOCK) to be created in a Coupling Facility (CF).
Similar[edit]
CA, Inc. licenses a product called 'Multi-Image Manager' (CA-MIM) which contains a component called 'Multi-Image Integrity' (MII) which can be used to implement similar functions to GRS.
References[edit]
- ^IBM Knowledge Center: https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.ieae200/ieae200294.htm
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