Traditional (B*-tree) indexes are most useful on columns with a significant amount of variety in their data. For instance, a column that indicates whether a company is a current client with a Y or N value would be a poor choice for a traditional index and could actually slow down a query; a bitmap index […]
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In addition to running the data load processes at off-peak hours, you can take other steps to improve the load performance. The following steps all impact your overall database environment and must be coordinated with the database administrator. The tuning of a data load should not be allowed to have a negative impact on the […]
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Database links tell Oracle how to get from one database to another. If you frequently use the same connection to a remote database, a database link is appropriate. How a Database Link Works A database link requires Oracle Net Services (previously known as SQL*Net and Net8) to be running on each of the machines (hosts) […]
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In addition to the traditional options for tuning a workload using the File or Table choice, which allows you to specify a script or a table containing the T-SQL statements to tune, starting with SQL Server 2012, you can also specify the plan cache as a workload to tune. In this case, the DTA will […]
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For a large database, a materialized view may offer several performance benefits. You can use materialized views to influence the optimizer to change the execution paths for queries. This feature, called query rewrite, enables the optimizer to use a materialized view in place of the table queried by the materialized view, even if the materialized […]
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You can assign unique numbers, such as customer IDs, to columns in your database by using a sequence; you don’t need to create a special table and code to keep track of the unique numbers in use. You do this by using the CREATE SEQUENCE command, as shown here: This creates a sequence that can […]
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Events can be viewed in the Incident Manager. Most events that you address are cleared automatically from this page. What remains are events that do not automatically clear or ones that have not received a response from an administrator. Some events do not clear automatically because Cloud Control has no way of verifying whether the […]
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Two significant enhancements to partitioning introduced in Oracle 11g are reference partitioning and interval partitioning. Reference partitioning allows you to create a partition based on a column that is not in the table being partitioned, but rather is a foreign key reference to a different table. This can be useful for partitioning related tables in […]
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Over an application’s lifespan, its data very likely will move from one database to another or from one host to another. Therefore, it will simplify application maintenance if the exact physical location of a database object is shielded from the user (and the application). The best way to implement such location transparency is through the […]
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Oracle provides a fast index rebuild capability that allows you to re-create an index without having to drop the existing index. The currently available index is used as the data source for the index, instead of the table’s being used as the data source. During the index rebuild, you can change its STORAGE parameters and […]
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An emkey is an encryption key used to encrypt and decrypt sensitive data stored in the Repository, such as host and database passwords and preferred credentials, and consists of a random number generated during the installation of the Repository. When you install the first OMS, an emkey is copied from a table in the Repository […]
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When you enable block change tracking in Oracle 11g, Oracle tracks the physical location of all database changes for incremental backups. RMAN automatically uses the change tracking file to determine which blocks need to be read during an incremental backup, and directly accesses those blocks to back them up. When block change tracking is not […]
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