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Briefly describe concurrency execution?
Lock - based protocols
Locks
There are several modes in which a data item may be locked in this section we restrict our attention to two modes
Ø Shared
Ø Exclusive
T1 : lock - x(B );
read(B);
B:=B-50;
write(B);
unlock(B);
Lock-x(A);
read(A);
A:=A+50;
write(A);
unlock(A).
What are the properties in a relation ? In a relation Ordering of rows is immaterial and No two rows are identical.
Due date for May 8
write-set(T): Each data items that are written by a transaction T
Draw an ER diagram that represents the information described below. Show all entity sets, relationship sets, primary keys, and the mapping cardinality of the relationship sets.
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Saving Derived Attributes to Avoid Re-computation Data that is derived from other data should be stored in the computed form to avoid re-computation. For this, we could define
Write a query that display ename annual salary and comm from emp table
What are the uses of the information in the Data dictionary? The following information is directly taken from the Data dictionary: Information on fields displayed with
Extend your CREATE TABLE statement from problem 3 with referential integrity constraints. Updates and deletes on related rows are restricted. 6. From examination of the sample data
how oracle can be used
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