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what is a built-ina notation of identity is built-into the data model or programming language and no user-supplied identifier is needed this form of
what is a namea user-supplied name is used for identity this form of identity is used for files in file systems the user gives every file a name that
what is a valuea data value is used for identity this form of identity is used in relational systemseg the primary key value of a tuple recognize the
what are the several forms of identitya valueb namec
what is object identityan object retains its identity even if some or all the values of variables or explanations of methods change
what is disadvantage of multiple inheritancesthere is potential ambiguity if the similar variable or method can be inherited from more than one
what is dagthe class-subclass relationship is shown by a directed acyclic grapheg employees can be temporary or permanent we might be create
what are multiple inheritancesmultiple inheritances allow a class to inherit variables and methods from many super
what is substitutabilityany method of a class-say a can equally well be adjured with any object belonging to any subclasses b of a this
differentiate sub-class and super-classthe specialization of a class is known as subclasseseg employee is a subclass of person and teller is a
what is the use of keyword isathe use of keyword isa is to show that a class is a specialization of another
what is the main difference between read-only and update methodsa read-only method does not affect the values of a variable in an object whereas an
what is the major advantage of object-oriented programming paradigmthe ability to modify the explanation of an object without affecting the rest of
what is meant by object-oriented data modelthe object-oriented paradigm is based on encapsulation of data and code related to an object in to a one
what are the time stamps associated with each data itemw-timestamp q denotes the largest time stamp if any transaction that implemented write q
how the time stamps are implementeduse the value of the system clock as the time stamp that is a transactions time stamp is equivalent to the value
differentiate strict two phase locking protocol and rigorous two phase locking protocolin strict two phase locking protocol all exclusive mode locks
define garbage collectiongarbage may be formed also as a side effect of crashes periodically it is essential to find all the garbage pages and to add
what are the drawbacks of shadow-paging techniquethe drawbacks of shadow paging is-a commit overheadb data fragmentationc garbage
explain current page table and shadow page tablethe key idea behind the shadow paging method is to maintain two page tables during the life of the
define pagethe database is partitioned into some number of fixed-length blocks which are referred to as
define shadow pagingan alternative to log-based crash recovery method is shadow paging this technique requires fewer disk accesses than do the
what are uncommitted modificationsthe immediate-modification technique permits database modifications to be output to the database whereas the
what is meant by log-based recoverythe most widely used structures for recording database changes is the log the log is a sequence of log records
what is meant by buffer blocks and disk buffer the blocks residing temporarily in main memory are referred to as buffer blocksthe area of memory