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Explain Two phase locking protocol
A transaction is consider as to follow the two-phase locking protocol if all locking operations precede the first unlock operation in the transaction. Such type of transaction can be divided into two phases: and expanding or growing (first) phase, throughout which new locks on items can be acquired but none can be released; and a shrinking (second) phase, throughout which existing locks can be released but no new locks can be obtained. This two-phase protocol can make sure the serializability because all the data items needed by a transaction will be locked at the starting of the transaction and if other transaction needs to use those data items then it has to wait till they become unlocked.
Speedup Query Processing: A query that includes data at various sites can be split into sub-queries. These sub- queries can be implemented in parallel by various sites. Such parall
What is a value? A data value is used for identity. This form of identity is used in relational systems.eg: The primary key value of a tuple recognize the tuple.
What is primary Key Explain? Primary Key - Primary key is one of the candidate keys. It should be selected such in which its attribute values are never, or very rarely, chang
What is the max. no. Of structures that can be included in a table or structure. Nine.
write on the various type of relationalkey
explain cascading rollback
What is recursive closure? Why is it not possible to describe this operation in relational algebra? Recursive closure is applied to recursive relationship. An instance of rec
WRITE SHORT NOTES ON INDEX STRUCTURE OF FILES? There are two basic parts of indices 1. Ordered indices 2. Hash indices Every technique must be evaluated on the bas
What is B-Tree? A B-tree eliminates the redundant storage of search-key values .It permits search key values to appear only once.
With the help of an example display how records can be deleted and updated in QBE. (i) Increase Pay_Rate of employees along with the skill of ‘cook' by 10%. (ii) Delete employee
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