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Storage Management Subsystem is an optional feature of Multiple Virtual Storage which is used to improve the management of available disk space in the data center.
In Job control subsystem, normally the developer must specify allocation attributes of datasets, such as the size and location about the data sets, to the operating systems. If they don’t allocate files correctly, this can lead to wasted disk space, and makes it difficult to manage the Direct Access Storage Device in the data center.
Advantage of SMS:
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SMS managed datasets have several advantages,
1. Users are relieved of making decisions about the resource allocation of datasets, since it is handle by SMS.
2. SMS provides the capability of concentrating data sets of unlike devices.
3. SMS managed data sets cannot be deleted unless they are first uncataloged. Due to this extra step, erroneous deletion of data sets is minimized.
4. VSAM data sets created in an SMS environment offer more flexibility than those created through JCL in non-SMS environment.
SMS Constructs:
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With SMS, a new data set can have one or more of the following three constructs:
1. DATA CLASS: Contains the dataset attributes related to allocation of the data set.
2. MANAGEMENT CLASS: Contains the data set attributes related to the migration and backup of the data set. A management class can be assigned to a data set that also has a storage class assigned.
3. STORAGE CLASS: contains the data set attribute related to the storage occupied by the data set. A data set has a storage class assigned is defined as an “SMS-Managed data set.”Now a days there are many people who use internet for many purposes. Some use for chatting, some use for business purposes, and many more are used. There are many people who use net for download. Many download file are being uploaded in RapidShare. Only limited are free users and thy can't download many files continously. After each file download we have to wait minimum of 15 mins. So this makes everyone to get a sad state and so many people takes many days time to download the full software or movie or what ever thy need.
So there is a trick to download rapidshare files continously one after the other. The trick is Dynamic IP address. many people uses dynamic ip address and it's available in broadband. So each time we switch off and switch on the modem, a new ip address is generated. So this is the thing we can use for downloading files from rapidshare.
1. After downloading file from rapidshare, switch off the modem and wait for few mins
2. Then again switch on the modem, a new ip address is generated.
3. So now u start to download a new file.
4. This makes u not to wait for more time after each time download.
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Mainframe computers can process several million-program instructions per second. Large organizations rely on this room-size system to handle large program with huge volume of data. Mainframes are mainly used by Banks, Insurance companies, Finance companies, Airline and Railways reservation system and so on.
Mainframes have even more access to storage space and to input/output device. To work with these extra device mainframes also have more powerful PROCESSORS. This power is useful and required by large corporations who have large amounts of data to process. For example, large international banks who have millions of customer accounts to update regular will need very powerful machine to process and maintain the data.
FEATURES OF MAINFRAME OPERATING SYATEM :
1. Virtual Storage :
Virtual storage is a technique that lets a processor an amount of main storage that is larger than the actual amount of real storage. Virtual storage operating system transfer data between real storage and disk storage as they are needed.
2. Multiprogramming
Multiprogramming means computer can execute more that one Job(program) at a same time. Multiprogramming simply reclaims the CPU during the idle periods and allow another job to execute.
3. Spooling
Spooling manages the output device for application by intercepting output device and directing it to a disk device instead. Then, when program complete executing, the operating system collects its spooled print output and direct it to output device like printer. And another advantage is the execution speed, it is faster.
4. Batch processing
Batch processing means work is processed in a unit of work called Job. Job may have one or more programs to execute in sequencially.
5. Time-sharing
Time sharing is also called as Interactive processing, because it allow user to interact directly to the computer.