6 storage and file structures

The original copy of the modified data is called undo data.

6 storage and file structures

From the Administration page, click Tablespaces under Storage. This takes you to the Tablespaces page. The Results page shows all tablespaces, including the following information about each: Click the tablespace name for more information. Creating a Tablespace A particular user, groups of users, or an application may require its own tablespace for creating schema objects, rather than using the default USER tablespace.

To create a tablespace, follow the steps listed in this section. This exercise will also familiarize you with the various attributes that you can set, and possibly later modify, for a tablespace. Or, if you want to create a tablespace that is like an existing tablespace, select an existing tablespace.

Then from the Actions menu, select Create Like. The Create Tablespace General page appears. Did you notice the other options that are available from the Actions pull down menu? These are shortcuts for various tablespace operations.

Enter a name for the tablespace. For a dictionary managed tablespace, you must more actively manage extents and data 6 storage and file structures access is required for tracking them. Dictionary managed tablespaces are being deprecated. Oracle does not recommend their use.

Under the Type heading, select appropriate type. Permanent tablespaces store permanent database objects created by the system or users. Temporary tablespaces are for storing temporary segments, as would be created when SQL statements perform sorts. The preconfigured database already has a temporary tablespace.

You would create another temporary tablespace if you were creating a temporary tablespace group. Under normal circumstances, you should not need to create additional temporary tablespaces.

Undo tablespaces are used by the system to store undo information. You might want to create another undo tablespace, but only one undo tablespace can be the active one.

Again, you should not need to create additional undo tablespaces. However, if you want to switch the undo tablespace used by the database instance, then you can create a new undo tablespace and instruct the database to use it instead of the undo tablespace currently in use.

The undo tablespace no longer in use can be dropped later. Under Status, select Read Write. Read Write status means users can read and write to the tablespace after it is created. This is the default. If the tablespace is created read-only, then the tablespace cannot be written to until its status is changed to Read Write.

You would probably not create a tablespace as read-only, but rather change it to that status after you have written data to it that you do not want modified. If the tablespace is created offline, then no users can have access to it. You would probably not create a tablespace as offline, but rather you would change its status to offline to perform some maintenance on its underlying files.

In the Datafiles section of the page, you can add one or more datafiles to the tablespace. However, if you select Use bigfile tablespace, then the tablespace can have only one datafile. In the Add Datafiles page, enter a file name. Use the File Directory and File Size defaults. Your database should contain several other tablespaces with their associated datafiles or tempfiles.

Be aware that your operating system might impose limits on the number of datafiles contained in your Oracle database. Also consider that the number of datafiles, and how and where they are allocated can affect the performance of your database. Leave the Maximum File Size set to Unlimited.

You are returned to the Create Tablespace General page. Click the Storage property page. The Create Tablespace Storage page appears.6 Managing Database Storage Structures. Other storage structures that can exist in an Oracle database include the initialization parameter file, the password file, and backup files.

If the Storage Type is set to File System, then in the File Name field, enter a file name for the new redo log member. Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Chapter Storage and File Structure Overview of Physical Storage Media Magnetic Disks RAID Tertiary Storage Storage Access File Organization Organization of Records in Files Data-Dictionary Storage.

Key Points. The iOS file system contains two partitions. The OS partition contains the iOS operating system. Only iOS system data can be written to this location.

Chapter 6: Managing Database Storage Structures Back to Lesson List Purpose.

Performing Common Database Storage Tasks

In this chapter you will learn how to use Enterprise Manager to explore the structure of your database. In addition, you will learn how to make a number of changes to your database storage structure.

6 storage and file structures

Enter a file name in the File Name field on the Add Datafiles. 6 Managing Database Storage Structures. The Control File.

A control file tracks the physical components of the database and other control information. It is essential to the functioning of the database. As the user base grows, you can expand existing database storage structures or create additional ones.

For example, you might need to. File Structures A file is a collection of data stored on mass storage (e.g., disk or tape) Why on mass storage? too big to fit in main memory share data between programs backup (disks and tapes are less volatile than main memory) The data is subdivided into records (e.g., student in-.

Database storage structures - Wikipedia