• Even though multiple transactions may execute concurrently,
the system guarantees that, for every pair of transactions Ti and
Tj , it appears to Ti that either Tj finished execution before Ti
started or Tj started execution after Ti finished.Thus,each
transaction is unaware of other transactions executing
concurrently in the system.
• Since a transaction is a single unit, its actions cannot appear to
be separated by other database operations not part of the
transaction.
• Even a single SQL statement involves many separate accesses
to the database, and a transaction may consist of several SQL
statements. Therefore, the database system must take special
actions to ensure that transactions operate properly without
interference from concurrently executing database statements
• Even though multiple transactions may execute concurrently,the system guarantees that, for every pair of transactions Ti andTj , it appears to Ti that either Tj finished execution before Tistarted or Tj started execution after Ti finished.Thus,eachtransaction is unaware of other transactions executingconcurrently in the system.• Since a transaction is a single unit, its actions cannot appear tobe separated by other database operations not part of thetransaction.• Even a single SQL statement involves many separate accessesto the database, and a transaction may consist of several SQLstatements. Therefore, the database system must take specialactions to ensure that transactions operate properly withoutinterference from concurrently executing database statements
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