ASP.NET Web PDF Document Viewer/Editor Control Library

Even though the XYZConnection implementation suggested so far looks straightforward, it contains a severe bug: there is a race condition between the finalizer thread and the threads using the managed wrapper. It can cause a call to the finalizer even though the native handle is still needed. Do not even consider implementing a finalizer unless you understand how to avoid this bug. To understand the finalization timing problem, it is necessary to have a certain understanding of the garbage collection process and some of its optimization strategies. Key to understanding garbage collection is the distinction between objects and referencing variables. In this context, referencing variables can be tracking handles (T^), tracking references (T%), variables of reference types that use the implicitly dereferenced syntax (T), interior pointers, and pinned pointers. To simplify the following explanations, I will summarize all these kinds of referencing variables as references. The GC is aware of all references and also of all objects on the managed heap. Since auto_handle variables, gcroot variables, and auto_gcroot variables internally manage tracking handles, the runtime is indirectly aware of those, too. To determine the objects that are no longer used, the GC distinguishes between root references and non-root references. A root reference is a reference that can directly be used by managed code.

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Oracle-managed files, which were introduced in Oracle8i (and which we ll discuss shortly), simplify the administration of Oracle databases The Oracle Managed Files (OMF) feature eliminates the need for you to manage operating system files You simply specify your database operations in terms of database objects, without using filenames For example, suppose you create a tablespace called customer01 with a 500MB data file As you load more data into your database, Oracle will allocate new extents to the database tables by allocating space from the data file When the table uses up almost all of the initial 500MB space allocation, you need to enlarge the tablespace by adding a new data file to it You may alternatively increase the size of the existing data file by resizing it as well.

There are a few noteworthy items in the command that displays the header line: first, echo is used with the -e switch, which translates escaped three-digit number sequences contained in text into the corresponding ASCII character; in our case it translates the ANSI escape-character sequence into the escape character. Other escape values can be used to represent other special characters, such as the carriage return, tab, and backspace. The second item is the hostname variable, which is surrounded by variables that control color output. The first variable changes the output from the default color to white. Once

If you don t, the table can t increase in size, and any attempts to add data to it will result in an error Although the data itself is placed in actual data files, there is no direct link between the tables and indexes and the data files they are placed in These objects are only linked to the logical tablespace; it is the tablespace that is linked to the data files Thus, Oracle maintains a separation between the logical objects (such as tables) and the physical data files In other words, there is no direct connection during object creation or growth between the object and the data files it resides in You can create or move an existing table or index by specifically declaring the tablespace, but you can t specify a data file directly..

The OMF feature aims at relieving DBAs of their traditional file-management tasks. When you use the OMF feature, you don t have to worry about the names and locations of the physical files. Instead, you can focus on the objects you re creating. Oracle will automatically create and delete files on the operating system as needed. The OMF-based files are ideal for test and small databases, but if you have a terabyte-sized database with a large number of archived logs and redo logs, you need flexibility, which the OMF file system can t provide. OMF drastically simplifies both the initial database creation as well as the management tasks. If you want to use OMF with your database, read the discussion of OMF in 18, where you ll learn how to create and manage OMF-based files.