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Difference between direct and serial access?
Direct access refers to the ability to retrieve data from any point in a storage device directly, without having to sequentially access preceding data. This is common in random access memory (RAM) and solid-state drives (SSDs). Serial access, on the other hand, requires data to be accessed sequentially in the order it was stored, such as in magnetic tape drives. This difference impacts the speed and efficiency of data retrieval in storage systems.
Serial access secondary storage device?
name one access secondary device?
File accessing techniques in data management system?
Information is kept in files. Files reside on secondary storage. When this information is to be used, it has to be accessed and brought into primary main memory. Information in files could be accessed in many ways. It is usually dependent on an application.Sequential Access: A simple access method, information in a file is accessed sequentially one record after another. To process the with record all the 1-1 records previous to 1 must be accessed. Sequential access is based on the tape model that is inherently a sequential access device. Sequential access is best suited where most of the records in a file are to be processed. For example, transaction files.Direct Access: Sometimes it is not necessary to process every record in a file. It may not be necessary to process records in the order in which they are present. Information present in a record of a file is to be accessed only if some key value in that record is known. In all such cases, direct access is used. Direct access is based on the disk that is a direct access device and allows random access of any file block. Since a file is a collection of physical blocks, any block and hence the records in that block are accessed. For example, master files. Databases are often of this type since they allow query processing that involves immediate access to large amounts of information. All reservation systems fall into this category. Not all operating systems support direct access files. Usually files are to be defined as sequential or direct at the time of creation and accessed accordingly later. Sequential access of a direct access file is possible but direct access of a sequential file is not.Indexed Sequential Access: This access method is a slight modification of the direct access method. It is in fact a combination of both the sequential access as well as direct access. The main concept is to access a file direct first and then sequentially from that point onwards. This access method involves maintaining an index. The index is a pointer to a block. To access a record in a file, a direct access of the index is made. The information obtained from this access is used to access the file. For example, the direct access to a file will give the block address and within the block the record is accessed sequentially. Sometimes indexes may be big. So hierarchies of indexes are built in which one direct access of an index leads to info to access another index directly and so on till the actual file is accessed sequentially for the particular record. The main advantage in this type of access is that both direct and sequential access of files is possible.
Difference between direct and sequential access?
RAM or Random Access Memory is used for fast computer memory. The word "Random" is a bit of a misnomer, as there is nothing random about access to this memory. What it actually means is that you can select an address at "random", that is, any address within the capability of the memory, and read or write data to/from that address just as fast as you could read or write data to any other address. In other words, data stored anywhere in the memory can be accessed quickly. Serial memory is different in that access time depends upon where on the medium the data is stored. Examples are magnetic tape, optical disk, magnetic disk. "arbitary access" is not a term used in electronics that I can find. I think it is just another term for "random access".
Is direct access file ordered?
A direct access file, in most systems, refers to a file where individual records are retrieved directlly by using a record number to refer to a specific position in a file. The alternative is to reach the desired record by sequential access: Reading all the records from the beginning until you reach the desired position in the file. The records in the file do not have to be in any specific order.
