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Autonomous Transactions → different transactions try to modify the same row does one transaction wait for the other to complete. The … COMMIT; END LOOP; CLOSE c1; END; / Autonomous Transactions An autonomous transaction is an … independent transaction started by another transaction, the main transaction. Autonomous transactions do SQL … back again. The
Controlling Autonomous Transactions → rollback comprise the current transaction. To control autonomous transactions, use these statements … Rolling Back Autonomous Transactions Savepoints Avoiding Errors with Autonomous Transactions
Advantages of Autonomous Transactions → on, even if the main transaction rolls back. Autonomous transactions help you build modular, reusable … software components. You can encapsulate autonomous transactions in stored subprograms. An invoking
Retrying Transactions After Handling Exceptions → To retry a transaction after handling an exception that it raised, use this technique: Enclose the transaction in a sub-block that has an exception-handling part. In the sub-block, before the transaction starts, mark a savepoint. In the exception-handling part of the sub-block, put an exception handler that rolls back to the savepoint and then tries to correct the problem. Put the sub-block inside
Transactions → for transactions is a funds transfer from a savings account to a checking account. The transfer … transaction from executing, then the other statements must be rolled back. Transactions are one feature … principle of a transaction is \"all or nothing\": an atomic operation succeeds or fails as a whole. See Also: \" Transactions \"
10 Transactions → This chapter defines a transaction and describes how the database processes transactions. This … chapter contains the following sections: Introduction to Transactions Overview of Transaction Control … Overview of Transaction Guard Overview of Application Continuity Overview of Autonomous Transactions Overview of Distributed Transactions
Sample Transaction: Account Debit and Credit → To illustrate the concept of a transaction, consider a banking database. When a customer transfers money from a savings account to a checking account, the transaction must consist of three separate operations: Decrement the savings account Increment the checking account Record the transaction in the transaction journal Oracle Database must allow for two situations. If all three SQL statements maintain
Savepoints → A savepoint is a user-declared intermediate marker within the context of a transaction. Internally, the savepoint marker resolves to an SCN. Savepoints divide a long transaction into smaller parts. If you use savepoints in a long transaction, then you have the option later of rolling back work performed before the current point in the transaction but after a declared savepoint within the transaction.
Application Continuity Architecture → lost transactions and potentially diverged Violates protocols Fails to reproduce the same client
Overview of Distributed Transactions → A distributed database is a set of databases in a distributed system that can appear to applications as a single data source. A distributed transaction is a transaction that includes one or more statements that update data on two or more distinct nodes of a distributed database, using a schema object called a database link. A database link describes how one database instance can log in to another
In-Doubt Transactions → of in-doubt distributed transactions. After the failure is repaired and communication is … distributed transactions consistently on all involved nodes. In the event of a long-term failure … transactions that are in doubt because of the failure. This option enables the local database administrator to … Administrator's Guide to
Introduction to Transactions → assigns every transaction a unique identifier called a transaction ID. All Oracle transactions obey the … transactions. For example, if a transaction starts updating 100 rows, but the system fails after 20 … transaction is not visible to other transactions until the transaction is committed. For example … concurrently by another
Statement-Level Atomicity → Oracle Database supports statement-level atomicity, which means that a SQL statement is an atomic unit of work and either completely succeeds or completely fails. A successful statement is different from a committed transaction. A single SQL statement executes successfully if the database parses and runs it without error as an atomic unit, as when all rows are changed in a multirow update. If a SQL
System Change Numbers (SCNs) → A system change number (SCN) is a logical, internal time stamp used by Oracle Database. SCNs order events that occur within the database, which is necessary to satisfy the ACID properties of a transaction. Oracle Database uses SCNs to mark the SCN before which all changes are known to be on disk so that recovery avoids applying unnecessary redo. The database also uses SCNs to mark the point at which
Transaction Names → advantages: It is easier to monitor long-running transactions and to resolve in-doubt distributed … transactions. You can view transaction names along with transaction IDs in applications. For example, a
Table 10-2 Rollback to Savepoint Example → Enqueued Transactions Depending on the scenario, transactions waiting for previously locked
Overview of Transaction Guard → guarantee that it would not commit after being checked, permitting duplicate transactions and other … online and be charged twice for the same book. See Also: \" Introduction to Transactions \" Oracle
How Transaction Guard Works → This section explains the problem of lost commit messages and how Transaction Guard uses logical transaction IDs to solve the problem.
Transaction Guard: Example → session that failed. For each round trip from the client in which one or more transactions are committed … , the application can replay transactions when the error is recoverable and the last transaction on
Overview of Application Continuity → Application Continuity attempts to mask outages from applications by replaying incomplete application requests after unplanned and planned outages. In this context, a request is a unit of work from the application. Typically, a request corresponds to the DML statements and other database calls of a single web request on a single database connection. In general, a request is demarcated by the calls