Mainframe - Crucial Role in Modern Enterprise Computing

1. 00:00Yeah, hello, it's me again, Wolfram Greis from the European Mainframe Academy,
2. 00:06and in the next video clip, I want to talk about
3. 00:11z/OS components. z/OS is the main operating system running
4. 00:15on IBM mainframes and with this
5. 00:20clip, I want to talk about the components that are the most important
6. 00:24components, I don't talk about all of them, just the most important components
7. 00:29that are running in a z/OS environment.
8. 00:32And when we talk about these components, there are two components where
9. 00:37we talk a little later in more detail.
10. 00:41These two components have a direct interface to the users and these interfaces
11. 00:45on the one side, the top management we see Job Entry Subsystem.
12. 00:51Job Entry Subsystem is the component that is necessary
13. 00:56for running batch jobs for running so-called starter tasks.
14. 01:00I think Professor Brune already mentioned them, what are starter tasks,
15. 01:05and also z/OS users get in contact with JES without
16. 01:10having to know that. But other people who
17. 01:15want to submit so-called batch jobs, they need, in any
18. 01:20case, the interface to the Job Entry Subsystem.
19. 01:24We have another component that has a direct interface to the
20. 01:28users. This is the Data management and the IO supervisor.
21. 01:33This is where the data is managed to and
22. 01:39you have managed on the datasets and the datasets
23. 01:44reside on DASD.
24. 01:47DASD is the abbreviation, for Direct Access Storage
25. 01:51Device. In other environments, we just talk about disks, and also
26. 01:56in the mainframe environment, sometimes we talk about disks.
27. 02:01And now we have a set of components, these screened components,
28. 02:08the so-called supervisor and the supervisor can be seen as something
29. 02:12like a kernel in our operating system.
30. 02:16It's a base of 'z' operating system and we don't go into
31. 02:21more detail just to mention them here, we have an interrupt handler, as
32. 02:26the name states, it handles interrupts and interrupts are really important.
33. 02:31All stuff that is coming into an mainframe operating
34. 02:36system comes via interrupts.
35. 02:39We can say that the IBM 'z' mainframe is a
36. 02:44100 percent interrupt-controlledenvironment.
37. 02:47So all the work that comes into the
38. 02:52system and also works that ends within the system, all are controlled
39. 02:57by interrupts.
40. 02:59In the middle of the management of such an environment are the so-called
41. 03:03Address Spaces.
42. 03:06Professor Brune already mentioned them in the last video clip.
43. 03:09Address Spaces, there are different kinds of address spaces, one of the more important
44. 03:13address spaces as examples are the so-called Starter Tasks.
45. 03:17In other operating system environments, you will talk about
46. 03:22daemons. So a daemon is very
47. 03:27well compatible with starter tasks and in general the address spaces.
48. 03:31Again, there is a nice comparison, if you compare it with other
49. 03:36operating systems, you would talk about processes.
50. 03:39So a process on a Unix or Linux system for example
51. 03:44is comparable to an address space and the address spaces have to be
52. 03:49managed and the interface and the components that manages
53. 03:53these address spaces is a so-called dispatch off and on
54. 03:58the right side with these green rectangles, we
55. 04:02have program management, how programs are managed.
56. 04:05We have task management, task can be compared to other
57. 04:10system environments like threads.
58. 04:13A task is like a thread. So when we talk about multitasking in a
59. 04:18mainstream environment, it's the same as if you talk about multithreading
60. 04:22in a Unix or Linux environment.
61. 04:25And then we have the storage management and just to emphasize,
62. 04:30it has nothing to do with the disk management.
63. 04:34It's really the storage management within the
64. 04:39system and we have three subcomponents, it's
65. 04:44RSM, VSM, and the ASM. This is the Real Storage Manager (RSM) controlling
66. 04:48the real storage. It's Virtual Storage Manager
67. 04:54managing your virtual storage, and the Auxillary Storage Manager (ASM)
68. 04:59is the paging manager.
69. 05:02The last components are System Resource Manager and the Workload Manager.
70. 05:07These are really important subcomponents, the system
71. 05:11resource manager as the name states, controls system resources
72. 05:16and in very, very former days, it was the only component
73. 05:21to control such an environment.
74. 05:23Though in former days, we had a focus on resource management.
75. 05:29In between, we got the workloadmanager, workload manager is an
76. 05:33extension of these control management things
77. 05:38and the workload manager, as although the name states, controls some workloads
78. 05:43and it's really important because on our IBM mainframe,
79. 05:48normally they are running very different workloads, they are
80. 05:53running batch workloads, time-sharing, online workloads, databases,
81. 05:58transactions and so on. These are workloads and the workload manager
82. 06:02controls these workloads and in between, we talk about the so-called Goal
83. 06:07Mode. It means that we set the goals for each and every one of our
84. 06:11workloads and the workload manager tries to keep this goal
85. 06:17exactly as they are set, and they can do it normally really,
86. 06:21really very efficiently. So it's not uncommon in a mainframe environment that
87. 06:26we have for a longer interval, let's say, one or
88. 06:30two hours, 100 percent CPU utilization.
89. 06:34It's normally no problem at all because these different workloads have different
90. 06:38priorities and the workload manager controls who gets control of the
91. 06:42resources.
92. 06:45This was a very brief overview of
93. 06:50the z/OS components and this was this video clip for
94. 06:54these components. If you have any questions, remarks, and so on.
95. 06:57Please use the discussion forum on the HPI
96. 07:02platform. Thank you very much and see you again in the next video
97. 07:07clip.

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