SGA_TARGET Specifies the total size of all SGA components. If SGA_TARGET is specified, then the buffer cache (DB_CACHE_SIZE), Java pool (JAVA_POOL_SIZE), large pool (LARGE_POOL_SIZE), and shared pool (SHARED_POOL_SIZE) memory pools are automatically sized.Before you increase the size of your SGA, you must understand the effects on the physical memory of your system. If you increase [...]
Written by admin on December 6th, 2010 with comments disabled.
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The init.ora file in oracle database determines Oracle operating system environment attributes, such as memory allocated for statements, memory allocated for data,and other crucial performance-related parameters. In Oracle 10g there are now 1381 different initialization parameters .We will focuses on the key parameters that affect database performance. The key to an optimized Oracle database is [...]
Written by admin on December 6th, 2010 with comments disabled.
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When creating tables and indexes, note the following: 1. Specify automatic segment-space management for tablespaces This allows Oracle to automatically manage segment space for best performance. 2.Set storage options carefully Applications should carefully set storage options for the intended use of the table or index. This includes setting the value for PCTFREE. Note that using [...]
Written by admin on December 6th, 2010 with comments disabled.
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The PGA_AGGREGATE_TARGET specifies the total amount of session PGA memory that Oracle will attempt to allocate across all sessions. PGA_AGGREGATE_TARGET was introduced in Oracle 9i and should be used in place of the *_SIZE parameters such as SORT_AREA_SIZE. Also, in Oracle 9i, the PGA_AGGREGATE_TARGET parameter does not automatically configure ALL*_SIZE parameters. For example, both the [...]
Written by admin on December 5th, 2010 with comments disabled.
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The redo log buffer is a circular buffer in the SGA that holds information about changes made to the database. This information is stored in redo entries. Redo entries contain the information necessary to reconstruct, or redo, changes made to the database by INSERT, UPDATE, DELETE, CREATE, ALTER, or DROP operations. Redo entries are used [...]
Written by admin on December 5th, 2010 with comments disabled.
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The buffer cache is part of the System Global area(SGA). It holds copies of data blocks so as they can be accessed quicker by oracle than by reading them off disk. For many types of operations, Oracle uses the buffer cache to store blocks read from disk. Oracle bypasses the buffer cache for particular operations, [...]
Written by admin on December 5th, 2010 with comments disabled.
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DB_CACHE_SIZE is the first parameter to look at in the initialization parameter file because it’s the most crucial parameter in Oracle.The data cache hit ratio is the percentage of the data block accesses that occur without requiring a physical read from disk. DB_CACHE_SIZE it is the first parameter to look at in the initialization parameter [...]
Written by admin on December 3rd, 2010 with comments disabled.
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A backup is a representative copy of data. This copy can include important parts of a database such as the control file, redo logs, and datafiles. A backup protects data from application error and acts as a safeguard against unexpected data loss, by providing a way to restore original data. Backups are divided into physical [...]
Written by admin on November 30th, 2010 with comments disabled.
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Oracle8i and later has a great feature that stores information on long-running queries currently active in the V$SESSION_LONGOPS view. The following example shows the results of a query against V$SESSION_LONGOPS: SELECT username, sql_text, sofar, totalwork, units FROM v$sql, v$session_longops WHERE sql_address=address AND sql_hash_value=hash_value ORDER BY address, hash_value, child_number HROA select count(*) from winners w1, winners_backup [...]
Written by admin on November 23rd, 2010 with comments disabled.
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An inline view is a statement in the FROM-clause of another SELECT statement. In-line views are commonly used simplify complex queries by removing join operations and condensing several separate queries into a single query. This feature was introduced in Oracle 7.2.An example of inline view is given blow SELECT * FROM (select dept_no, count(*) emp_count [...]
Written by admin on November 8th, 2010 with no comments.
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