ASP.NET PDF Viewer using C#, VB/NET

The data dictionary tables describe the entire database: its logical and physical structure, its space usage, Tip its objects and their constraints, and user information. You can t access the data dictionary tables directly; instead, you re given access to views built on them. You also can t change any of the information in the data dictionary tables yourself. Only Oracle has the capability to change data in the data dictionary tables. When you issue a query involving the CITIES column in a table named EMPLOYEES, for example, the database will consult various data dictionary tables to verify that the table and the column exist, and to confirm that the user has the rights to execute that statement. As you can imagine, a heavily used OLTP database will require numerous queries on its data dictionary tables during the course of a day.

barcode fonts for excel 2016, how to make barcodes in excel 2016, barcode fonts for excel 2010 free, random barcode generator excel, how to make barcodes in excel 2010, barcode in excel einlesen, excel barcode add-in, how do i create a barcode in excel 2007, download barcode font for excel 2010, active barcode excel 2010,

The Oracle super user SYS owns most of the data dictionary tables (though some are created under the system username), and they are stored in the System tablespace.

true, false 'a'

Oracle recommends that you analyze both the data dictionary and the dynamic performance tables (also Tip referred to as fixed tables) on a regular basis to improve performance. 21 shows you how to analyze these tables.

By default, Oracle Database 10g automatically tunes the undo retention period. Oracle recommends that Tip you not set a value for the UNDO_RETENTION parameter unless your system has Flashback or LOB retention requirements.

You may find it useful to have two versions of this script: one that outputs the elapsed time in days and the other that outputs it in seconds.

In automatic undo management, the database is in charge of creating, allocating, and deallocating the undo segments as necessary. You can query the DBA_ROLLBACK_SEGS view to find out which of your undo segments are online, as shown here: SQL> SELECT segment_name, tablespace_name, status FROM dba_rollback_segs; The undo segments created under automatic undo management are structurally similar to the traditional rollback segments. The big difference, of course, is that Oracle will automatically create them and drop them as necessary. Oracle creates a predetermined number of undo segments when you create the undo tablespace, and it may bring all or some of them online when you start up the instance. Oracle will always try to assign each transaction its own undo segment, and it will create more undo segments if necessary, based on the transactions in the database. During a day s time, it s common for Oracle to increase and decrease the number of undo segments based on its own internal algorithms and the level of database activity. If the UNDO_MANAGEMENT parameter is set to AUTO and you fail to create a specific undo tablespace for storing undo information, Oracle will still create undo records in a default tablespace named SYS_UNDOTBS, with a default size of around 200MB. The following SQL script will tell you the location and size of the undo tablespace in your database: SQL> SELECT file_name, bytes 2 FROM dba_data_files 3 WHERE tablespace_name='UNDOTBS'; FILE_NAME BYTES ---------------------------------------------------/u01/orcl/oradata/undotbs01_01.dbf 209715200 SQL>

Oracle recommends that you size your undo tablespace with the help of the Undo Advisor. However, if you ve just created your database, the Undo Advisor won t have enough historical data about undo requirements to help you. Oracle makes the following recommendations for a new database. Initially, create a small-sized (approximately 500MB) undo tablespace, with the AUTOEXTEND data file attribute set to ON, thus allowing an automatically extensible tablespace. The tablespace will automatically grow, both to support a growing number of active transactions as well as the growing length of transactions in the database. After the database has run for a reasonable length of time, use the Undo Advisor to get recommendations for sizing the undo tablespace. Use the maximum time allowed in the Analysis Time Period field. You can use the Longest-Running Query length shown in the OEM Undo Management page for this purpose. You must also specify a value for the New Undo Retention field based on your Flashback requirements. If you wish to be able to flash back your tables, for example, for a period of 24 hours in the past, use 24 hours as the value for this field.

The main reason for fixing the size of the undo tablespace (rather than keeping it auto-extensible) is to prevent a single runaway query from taking up all the free space in the database.

Using these two values (those in the Analysis Time Period field and the New Undo Retention field), the Undo Advisor will recommend the appropriate undo tablespace size. You can then add about 20 percent to the size you arrive at as a safety margin, and make the undo tablespace a fixedsize tablespace by disabling the AUTOEXTEND attribute.

1L 1U 1LL 1ULL 1.0f, -1e-4f 1.0, -1e-4 L'a'