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The DBA_EXP_FILES view shows details about all the all export files in the database, including the export-file names, name of the user who executed the export, and the time stamp of the export session.

Here is a more detailed explanation of the elements that make up this file. The first few lines set up some path and mail-logging variables.

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In discussing the Oracle database architecture, you can make a distinction between the physical and logical structures. You don t take all the data from the tables of an Oracle database and just put it on disk somewhere on the operating system storage system. Oracle uses a sophisticated logical view of the internal database structures that helps in storing and managing data properly in the

Like the native address-of operator (&), the prefix operator % can be misused. The following code shows an obvious example: FileStream^ GetFile() { FileStream fs("sample.txt", FileMode::Open); return %fs; } This function defines a local FileStream variable and returns the tracking handle wrapped by that variable. When that function returns, the local variable leaves its scope, and the FileStream s Dispose method is called. The tracking handle that is returned to the caller refers to an object that has just been disposed. Accessing an object whose destructor has just been called is obviously not a good idea. This is true for native as well as managed objects. However, access to a destroyed native object typically has more undesired effects than access to a destroyed managed object.

physical data files. By organizing space into logical structures and assigning these logical entities to users of the database, Oracle databases logically separate the database users (who own the database objects, such as tables) from the physical manifestations of the database (data files and so forth). The following sections discuss the various logical and physical data structures.

Oracle databases use a set of logical database storage structures in order to manage the physical storage that is allocated in the form of operating system files. These logical structures, which primarily include tablespaces, segments, extents, and blocks, allow Oracle to control the use of the physical space allocated to the Oracle database. Taken together, a set of related logical objects in a database is called a schema. Remember that Oracle database objects, such as tables, indexes, and packaged SQL code, are actually logical entities. Dividing a database s objects among various schemas promotes ease of management and a higher level of security. Let s look at the logical composition of an Oracle database from the bottom up, starting with the smallest logical components and moving up to the largest entities: Data blocks: The Oracle data block is at the foundation of the database storage hierarchy and is the basis of all database storage in an Oracle database. A data block consists of a number of bytes of disk space in the operating system s storage system. All Oracle s space allocation and usage is in terms of Oracle data blocks. Extents: An extent is two or more contiguous Oracle data blocks, and this is the unit of space allocation. Segments: A segment is a set of extents that you allocate to a logical structure like a table or an index (or some other object). Tablespaces: A tablespace is a set of one or more data files, and usually consists of related segments. The data files contain the data of all the logical structures that are part of a tablespace, like tables and indexes. The following sections explore each of these logical database structures in detail.

The smallest logical component of an Oracle database is the data block. Data blocks are defined in terms of bytes. For example, you can size an Oracle data block in units of 2KB, 4KB, 8KB, 16KB, or 32KB (or even larger chunks), and it is common to refer to the data blocks as Oracle blocks. The storage disks on which the Oracle blocks reside are themselves divided into disk blocks, which are areas of contiguous storage containing a certain number of bytes for example, 4,096 or 32,768 bytes (4KB or 32KB; each kilobyte has 1,024 bytes).

The next two lines configure the amount of logging information that your log files will receive: