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Active Session History Reports for Oracle RACThis section describes Active Session History (ASH) reports for Oracle RAC under the following topics:Overview of ASH Reports for Oracle RACASH Report for Oracle RAC: Top Cluster EventsASH Report for Oracle RAC: Top Remote InstanceSee Also:Oracle Database Performance Tuning Guide for more information about ASH reportsOverview of ASH Reports for Oracle RACASH is an integral part of the Oracle Database self-management framework and is useful for diagnosing performance problems in Oracle RAC environments. ASH report statistics provide details about Oracle Database session activity. Oracle Database records information about active sessions for all active Oracle RAC instances and stores this data in the System Global Area (SGA). Any session that is connected to the database and using CPU is considered an active session. The exception to this is sessions that are waiting for an event that belongs to the idle wait class.ASH reports present a manageable set of data by capturing only information about active sessions. The amount of the data is directly related to the work being performed, rather than the number of sessions allowed on the system.ASH statistics that are gathered over a specified duration can be put into ASH reports. Each ASH report is divided into multiple sections to help you identify short-lived performance problems that do not appear in the ADDM analysis. Two ASH report sections that are specific to Oracle RAC are Top Cluster Events and Top Remote Instance as described in the next two sections.ASH Report for Oracle RAC: Top Cluster EventsThe ASH report Top Cluster Events section is part of the Top Events report that is specific to Oracle RAC. The Top Cluster Events report lists events that account for the highest percentage of session activity in the cluster wait class event along with the instance number of the affected instances. You can use this information to identify which events and instances caused a high percentage of cluster wait events.ASH Report for Oracle RAC: Top Remote InstanceThe ASH report Top Remote Instance section is part of the Top Load Profile report that is specific to Oracle RAC. The Top Remote Instance report shows cluster wait events along with the instance numbers of the instances that accounted for the highest percentages of session activity. You can use this information to identify the instance that caused the extended cluster wait period.
Active Session History Reports for Oracle RAC