OCA /OCP Oracle Database 11g A ll-in-One Exam Guide- P92:There is an ever increasing demand for staff with IT industry certification. The benefits to employers are significant—they can be certain that staff have a certain level of competence—and the benefits to the individuals, in terms of demand for their services, are equally great. Many employers are now requiring technical staff to have certifications, and many IT purchasers will not buy from firms that do not have certified staff. | OCA OCP Oracle Database 11g All-in-One Exam Guide 866 The manageability infrastructure provided with Oracle Database 11g can be used to automate a significant amount of the database administrator s day-to-day work. With earlier releases monitoring the database in order to pick up developing problems before they became critical took too much time. Identifying and diagnosing performance issues was not only time-consuming but also required much skill. Use of the Alert system and the diagnostic advisors installed as standard in every 11g database frees the DBA from the necessity of devoting a large amount of effort to this work. The Automatic Workload Repository Oracle collects a vast amount of statistical information regarding performance and activity. This information is accumulated in memory and periodically written to the database to the tables that make up the Automatic Workload Repository the AWR. The AWR exists as a set of tables and other objects in the SYSAUX tablespace. The AWR is related to the data dictionary but unlike the data dictionary the AWR is not essential for the database to function though it may be necessary for it to function well . Data is written to the AWR stored for a while and eventually overwritten with more recent information. Gathering AWR Statistics The level of statistics gathered is controlled by the instance parameter STATISTICS. LEVEL. This can be set to BASIC or to TYPICAL which is the default or to ALL. The TYPICAL level will force the collection of all the statistics that are needed for normal tuning without collecting any whose collection would impact adversely on performance. The BASIC level will disable virtually all statistics with no appreciable performance benefit. The ALL level will collect extremely detailed statistics on SQL statement execution these may occasionally be necessary if you are doing advanced SQL statement tuning but they may cause a slight performance drop while being collected. Statistics are accumulated .
