Explain Transaction Transparency ?
https://www.computersprofessor.com/2016/07/explain-transaction-transparency.html
Which
allows a transaction to update data at more than one network: the basic
concepts are :
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A remote request is a single SQL
statement access the data that are to be processed by a single remote data
base processor.
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A remote transaction composed of
several request, access data at a single remote site.
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A
distributed request :
Let a single SQL statement reference data located at several different local
( or) remote DP sites.
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A distributed transaction composed
of several distribution requests access data at different sites.
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Two phase commit protocol
:
Two –phase commit protocol requires DO–UNDO–REDO protocol.
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DO performs the operations &
records the “before “ & after values in the transaction log.
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UNDO reverses on operation.
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REDO redoes on operation.
Two
phase commit protocol is implemented in two phases.
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Phase 1 : preparation :
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coordinators sends a prepare to
commit message to all subordinates.
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subordinates receive the message
& send acknowledgement.
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It all nodes are prepared to commit
the transaction goes to phased or it aborts the transaction.
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Phase 2 : Final commit :
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1.The
coordinates board costs a commit message to all subordinates & waits for
the replies.
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2.
Each subordinate receive the commit message & then update the database
using the DO protocol.
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3.
The subordinate reply with a committed (or) not committed message to the
coordinates.
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4.
If one (or) more subordinates didn’t commit, the coordinator sends an short
message three by for them to UNDO as changes.
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