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Oracle - What
is a READ WRITE transaction in Oracle? - April 10, 2009
at 11:00 AM
What is a READ WRITE transaction in
Oracle?
The read consistency is set at the statement level in a READ
WRITE transaction.
A logical snapshot of the database is created
at the beginning of the execution of each statement and released at
the end of the execution.
Therefore, the reads within a single
statement get consistent data from the database.
Eg:
Suppose a query takes 10 minutes to be executed.
Then a
database snapshot is taken for this query for 10 minutes due to
which for a subquery of this query, data consistency is maintained
at any point within 10 minutes.
Therefore, any updates to the
database in this timespan wouldn’t make any difference to the result
of this query.
By default, all transactions are started as
READ WRITE transactions.
Also read
PL/SQL is a transaction processing language that offers the
following advantages............
The parser scans the statement and breaks it into logical units
such as keywords, identifiers and operators, A query or a sequence
tree is built using the units above. This is done to transform the
source data into the format required by the result set.............
READ COMMITTED: If row locks are obtained by a certain
transaction, then any other transaction that contains DML needs to
wait until the row locks have been released by that particular
transaction.............
Oracle server implicitly starts a new transaction with the
following two conditions: The first executable statement of a new
user session automatically starts a new transaction.............
Following commands could be run to explicitly end the current
transaction: COMMIT and ROLLBACK............
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