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Oracle Internal

This category contains 5 posts

Oracle SQL Plan Baseline

Oracle Database SQL Plan Baseline (11g) First, the basic concept Oracle 11g began to provide a new method of fixed operating plan that is SQL plan baseline; it can be summarized in the following two: Provide stable operation plan to the SQL Statement. Prevent the operating environment or object statistics and other factors change have … Continue reading

To dump the Oracle Database data file header information through oracle event

Direct use of the data file header dump, you can not query the data file header information Directly through the sql command 1) It is not any useful information, as follows: Block 1 (file header) not dumped:use dump file header command – From the first sentence can not see the data file DUMP out. 2) … Continue reading

Oracle Commit

Oracle Commit Oracle Commit Work Process before commit Oracle revocation the undo record in the buffer of the SGA, the undo record contains the old value update and delete table row. Oracle redo log buffer in the SGA generated redo log record Oracle Database modify the SGA buffer during commit The redo records on the … Continue reading

Oracle SCN – The Concept

1. What is scn? SCN to identify the database at a precise moment commit. When a transaction is committed, it is given a unique identifier transaction SCN. SCN at the same time as the internal clock mechanism for Oracle database, can be seen as logical clocks, each database has a global SCN generator. SCN (System … Continue reading

Oracle SCN – In Details

SCN(system change number) in Oracle Database System and the time of our lives meaning are the same, SCN is Oracle in time number. Why Oracle not use Operation System time to define it? If I perform a DML in the US New York Time at 8:00, and then modify the OS time of the machine … Continue reading