Who is using undo tablespace in oracle

Can anybody help me on "what all users are using the undo tablespace and how much" in oracle database 11g r2. Undo is not used by users directly but by statements which modify many database blocks. Try to search for session which generates a lot of redo. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Oracle Undo tablespace users Ask Question.

Asked 8 years, 7 months ago. Active 8 years, 5 months ago. Viewed 24k times. Improve this question. Hitesh Chouhan Hitesh Chouhan 5 5 gold badges 12 12 silver badges 21 21 bronze badges. After the database has been up for a while, you can view the Longest Running Query field on the Undo Management page of Enterprise Manager. For example, if you expect to run Flashback Queries for up to 48 hours in the past, your flashback requirement is 48 hours.

You then take the maximum of these two undo retention values and use that value to look up the required undo tablespace size on the Undo Advisor graph. You can activate the Undo Advisor by creating an undo advisor task through the advisor framework.

The following example creates an undo advisor task to evaluate the undo tablespace. The name of the advisor is 'Undo Advisor'. After you have created the advisor task, you can view the output and recommendations in the Automatic Database Diagnostic Monitor in Enterprise Manager.

Oracle Database 2 Day DBA for more information on using advisors and "Using the Segment Advisor" for an example of creating an advisor task for a different advisor. This section describes the various steps involved in undo tablespace management and contains the following sections:. There are two methods of creating an undo tablespace. The second method is used with an existing database.

You cannot create database objects in an undo tablespace. It is reserved for system-managed undo data. Oracle Database enables you to create a single-file undo tablespace. Single-file, or bigfile, tablespaces are discussed in "Bigfile Tablespaces".

You can create more than one undo tablespace, but only one of them can be active at any one time. However, since most aspects of undo tablespaces are system managed, you need only be concerned with the following actions:. If an undo tablespace runs out of space, or you want to prevent it from doing so, you can add more files to it or resize existing datafiles. An undo tablespace can only be dropped if it is not currently used by any instance. All contents of the undo tablespace are removed.

You can switch from using one undo tablespace to another. If any of the following conditions exist for the tablespace being switched to, an error is reported and no switching occurs:. The database is online while the switch operation is performed, and user transactions can be executed while this command is being executed. When the switch operation completes successfully, all transactions started after the switch operation began are assigned to transaction tables in the new undo tablespace.

The switch operation does not wait for transactions in the old undo tablespace to commit. In this mode, existing transactions can continue to execute, but undo records for new user transactions cannot be stored in this undo tablespace.

From then on, the undo tablespace is available for other instances in an Oracle Real Application Cluster environment. Use this statement with care because there may be no undo tablespace available. The Oracle Database Resource Manager can be used to establish user quotas for undo space. You can specify an undo pool for each consumer group. An undo pool controls the amount of total undo that can be generated by a consumer group.

When the total undo generated by a consumer group exceeds its undo limit, the current UPDATE transaction generating the undo is terminated. No other members of the consumer group can perform further updates until undo space is freed from the pool.

If you are currently using rollback segments to manage undo space, Oracle strongly recommends that you migrate your database to automatic undo management. Oracle Database provides a function that provides information on how to size your new undo tablespace based on the configuration and usage of the rollback segments in your system. DBA privileges are required to execute this function:.

This section lists views that are useful for viewing information about undo space in the automatic undo management mode and provides some examples. In addition to views listed here, you can obtain information from the views available for viewing tablespace and datafile information. Please refer to "Viewing Datafile Information" for information on getting information about those views.

Oracle Database also provides proactive help in managing tablespace disk space use by alerting you when tablespaces run low on available space. Please refer to "Managing Tablespace Alerts" for information on how to set alert thresholds for the undo tablespace. To prevent excessive alerts, the long query alert is issued at most once every 24 hours. When the alert is generated, you can check the Undo Advisor Page of Enterprise Manager to get more information about the undo tablespace. The following dynamic performance views are useful for obtaining space information about the undo tablespace:.

Statistics are available for undo space consumption, transaction concurrency, the tuning of undo retention, and the length and SQL ID of long-running queries in the instance. Each row in the view contains statistics collected in the instance for a ten-minute interval. Your email address will not be published.

Check Undo Tablespace Usage You can use the following query to check the undo tablespace usage. Author: dbtut We are a team with over 10 years of database management and BI experience. Share Facebook Twitter LinkedIn. Leave a Reply Cancel reply Your email address will not be published.