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Documentation
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In multi-user systems, many users may update the same information at the same time. Locking allows only one user to update a particular data block; another person cannot modify the same data.
The basic idea of locking is that when a user modifies data through a transaction, that data is locked by that transaction until the transaction is committed or rolled back. The lock is held until the transaction is complete - this known as data concurrency.
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The full list of Oracle parallel execution features currently includes the following: Parallel Query, Parallel DML, Parallel DDL, Parallel Data Loading, Parallel Recovery, Parallel Replication, How Parallel Execution Works.
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Without proper safeguards, applications are vulnerable to various forms of security attack. One particularly pervasive method of attack is called SQL injection. Using this method, a hacker can pass string input to an application with the hope of gaining unauthorized access to a database.
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This article will introduce the reader to the basics of auditing an Oracle database. Oracle's RDBMS is a functionally rich product and there are a number of auditing alternatives available to the reader. Because auditing Oracle is such a huge subject, doing all of it justice would take an entire book, so this paper will cover the basics of why, when and how to conduct an audit. It will also use a couple of good example cases to illustrate how useful Oracle audit can be to an organization.
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In Part 1 of this article, we discussed some of the basics of data encryption, including what is encryption, encryption algorithms, what type of encryption scheme to use when, and more. Now, let’s take a look at the other side of encryption: decryption and its elements.
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Oracle's LogMiner utility has been around for several years now, and it originally appeared as a new feature (as opposed to being an improvement of something else). Each major release of Oracle typically ushers in a new set of features, some of which are actually useful and can make your job as a DBA even easier. The "buzz" on LogMiner has worn off. Part of its initial allure was its ability to help DBAs recover data by generating SQL "undo" statements from the online (and archived) redo logs. Part of what made LogMiner undesirable to use is its interface and reliance on executing a package containing a laundry list of options.
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In many database configurations, the DBA will choose to allow their temporary tablespace (actually the tempfile(s) for the temporary tablespace) to autoextend. A runaway query or sort can easily chew up valuable space on the disk as the tempfiles(s) extends to accommodate the request for space. If the increase in size of the temporary tablespace (the tempfiles) gets exceedingly large because of a particular anomaly, the DBA will often want to resize the temporary tablespace to a more reasonable size in order to reclaim that extra space
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Both system failures and human blunders continually happen, but you just might be able to tread water if you implement Oracle’s flash features.
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Oracle have now included support for many ANSI SQL/99 features including ANSI compliant joins, and there are several advantages in using this new syntax.
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For data-in-motion-type encryptions, in which the data is encrypted to be sent across wire to reduce chances of eavesdropping, the asymmetric encryption is usually used, due to two primary reasons. First, the single key use in symmetric key encryption is not practical; and second, the length of time for which the encryption key must be in use is very short, so much smaller encryption keys can be used. Even if the intruder cracks the key, the data is already transmitted, reducing chances of compromise. In case of encryption of data-at-rest, the key is held for a much longer duration, so a longer key is necessary. To balance the need to reduce key length and reduce risk of exposure, asymmetric encryption schemes are used in data-at-rest.
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In a previous article on LogMiner, the steps for setting up your environment to use this tool were shown. Oracle's documentation lists several ways LogMiner can be used to recover lost data. Generally, "lost" in this case means a user error induced type of loss. Under the appropriate conditions, you can strike gold with LogMiner. In other situations, you run the risk of striking out. This article investigates a scenario that LogMiner may or may not be able to recover or fix. Let's start off by reviewing what Oracle says LogMiner can do.
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Books
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Packt is pleased to announce,Oracle 11g Streams Implementer's Guide a new book written by Ann L. R. McKinnell and Eric Yen. This book will serve as an excellent companion to the Oracle Streams Administration Guide. It also explains in detail the various components of Oracle Streams and how they work together.
Oracle Streams 11g, a built-in feature of the Oracle database, is a critical data replication and integration feature. It provides flexible infrastructure that meets a wide variety of information sharing needs. Oracle Streams enables the propagation of data, transactions and events in a data stream either within a database or from one database to another.
Oracle database administrators will get a clear and concise explanation of Oracle Streams components and concepts. They will also find various design considerations and techniques to understand what is needed to initiate building.
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Software
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Ignite is the only tool that answers the key questions yielding highest impact on database performance in both development and production operation:
Which individual SQL statements are most responsible for delays at any current or historical period?
Which database resources are the biggest bottlenecks, and exactly how much time will be gained by fixing each problem?
How can my application SQL be optimized to keep it from slowing down inside the database?
How long are specific transactions, users, applications and systems waiting on each Oracle resource at any time?
Can this bottleneck be addressed by database tuning, or should it be pushed back to the developer or a network administrator?
If you are a development or production DBA who needs expert tools to match your expertise, or a manager of DBAs who must do more without expanding, DBFlash is the best in class with highly cost effective, specialized help.
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Documentation
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Since an Oracle database consists of several interrelated parts, recovering such a database is done through a process of elimination. Identify which pieces work, then recover the pieces that don't work. The following recovery guidefollows that logic and works regardless of the chosen backup method. It consists of a flowchart and a procedure whose numbered steps correspond to the elements in the flowchart.
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In general, backup and recovery refers to the various strategies and procedures involved in protecting your database against data loss and reconstructing the database after any kind of data loss.
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While it is true that data storage prices (disks) have fallen dramatically over the last decade (and continue to fall rapidly), Oracle data compression has far more appealing benefits than simply saving on disk storage cost. Because data itself can be highly compressed, information can be fetched off of the disk devices with less physical IO, which radically improves query performance under certain conditions.
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Category: PHP
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Updated:01/13/2010
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If you're new to PHP or Oracle, working out how to handle dates efficiently can be tricky. You may have strategies, which you've applied successfully on other platforms, but will they fit to the combination of Oracle and PHP?
This Oracle+PHP recipe should help you understand the functionality, available in both PHP and Oracle, for working with dates and times and how they relate to each other. In doing so, it should help you decide where to draw line in deciding which technology will handle what, and answer questions like "Do I calculate the difference between these two dates in PHP or Oracle?"
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Oracle often comes head to head with SQL Server and DB2 in DBMS evaluations. While Oracle's price tag may be higher, many users claim its functionality is preferred over that of its competitors, particularly in large-enterprise environments. Judge for yourself. This crash course will help you research Oracle technologies or get started with your own Oracle DBMS. It will bring you up to speed on Oracle DBMS basics for versions 8.x through 9.x, and provide you with an overview of Oracle10g's new tools and features.
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This chapter describes the nature of and relationships among the logical storage structures in the Oracle database server.
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This is the first in a series introducing some of the new tracing concepts and options within Oracle. This installment focuses on the new CLIENT_IDENTIFIER environment variable that can be assigned to sessions.
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