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what is called mirroringthe simplest approach to introducing redundancy is to duplicate each disk this method is called mirroring or
what is the use of raida variety of disk-organization methods collectively called redundant arrays of independent disks are used to better the
what are called journaling file systemsfile systems that support log disks are known as journaling file
what is a block and a block numbera block is a contiguous sequence of sectors from a single track of one platter every request specifies the address
what is meant by mean time to failurethe mean time to failure is the amount of time that the system could run continuously without
what is meant by data-transfer ratethe data-transfer rate is the rate at which data can be retrieved from or kept to the
define average latency timethe average latency time of the disk is one-half the time for a full rotation of the
define rotational latency time the time spent waiting for the sector to be accessed to appear under the head is known as the rotational latency
define average seek timethe average seek time is the average of the seek times calculated over a sequence of random
define seek timethe time for repositioning the arm is known as the seek time and it enhances with the distance that the arm is known as the seek
define access timeaccess time is the time from when a read or write request is issued to when data transfer
what is called remapping of bad sectors if the controller detects that a sector is injured when the disk is initially formatted or when an attempt is
what are the types of storage devicesprimary storagesecondary storagetertiary storagevolatile storagenonvolatile
what are called jukebox systemsjukebox systems have a few drives and numerous disks that can be loaded into single of the drives
define query optimizationquery optimization refers to the process of search the lowest -cost method of evaluating a given
what is an indexan index is a structure that helps to place desired records of a relation quickly without probing all
what is 2nfa relation schema r is in 2nf if it is in 1nf and every non-prime attribute a in r is fully functionally dependent on primary
define canonical covera canonical cover fc for f is a set of dependencies like f logically implies all dependencies in fc and fc logically shows all
what is meant by normalization of datait is a process of examining the given relation schemas based on their functional dependencies fds and primary
what is meant by computing the closure of a set of functional dependencythe closure of f denoted by f is the set of functional dependencies logically
what are axiomsaxioms or rules of inference give a simpler technique for reasoning
explain trivial dependencyfunctional dependency of the form alpha -gtbeta is trivial if alpha c beta trivial functional dependencies are satisfied by
what are the uses of functional dependencies to test relations to see whether they are legal under a given set of functional dependenciesto state
what is meant by functional dependenciesconsider a relation schema r and alpha c r and beta c r the functional dependency alpha -gtbeta holds on
what is first normal formthe domain of attribute must contain only atomic simple indivisible