September 2007
Sun Education and 310-019 and SCJA and Article
JDBC: Free Article for SCJA Exam from uCertify
This free article for SCJA certification exam is provided by uCertify that will help you to prepare and excel in exam CX310-019. This exam measures your in-depth knowledge and skills in designing application using Java technology.
JDBC
The introduction of the Java language is required before introducing the concept of JDBC. Java is an object-oriented programming language. It incorporates all the objected-oriented concepts such as polymorphism, abstraction, encapsulation, etc. Java is a platform independent language because it can run on different operating systems. Java syntactically resembles C and C++, but it is simpler than the two, as it does not contain pointers and multiple inheritance. Both pointers and multiple inheritance seem complex to the application developer. Java has some drawbacks too. It does not provide much facility for developing GUI (graphical user interface) applications. The earlier version of Java did not contain any support for database access. This was the major drawback of this language, as in today’s world, keeping and managing databases is quite important. To remove this drawback, Sun Microsystems has introduced a new interface known as Java Database Connectivity (JDBC). JDBC provides database connectivity to Java applications.
JDBC Interface
JDBC stands for Java Database Connectivity. It provides database access to Java applications. The JDBC API interfaces are used to connect to the database and execute all types of SQL statements. The JDBC API interfaces can execute normal SQL statements, dynamic SQL statements, and stored procedures that take both IN and OUT parameters. The section below provides a description of various JDBC API interfaces.
Callable Statement Interface: This interface provides methods for executing stored procedures that return OUT parameter values. The CallableStatement object inherits the PreparedStatement object, adds various methods for registering parameters to be OUT parameters, and provides methods to get the parameters passed back from the stored procedure.
Connection Interface: This provides database connection to Java applications. It can be used to create various Statement objects for executing SQL statements and stored procedures. It also provides the facility to set the transaction properties for the connection.
Database MetaData: This interface provides various methods for obtaining the information about the database. It provides listing of tables for a specific database, primary keys, columns, and other information related to specific tables.
Driver Interface: This is a database specific Driver object, which the JDBC vendor provides. It contains information about connecting Java applications to the database. It also provides information about the database, such as version of the database, etc.
Prepared Statement Interface: This interface supports the execution of dynamic SQL statements and stored procedures. It allows setting various parameters in dynamic statements with specified data values.
Note: Dynamic statements are those statements whose values are not known at the time of creation.
Result Set Interface: This object is used to get information from a SQL SELECT statement. The SQL SELECT statement returns the cursor, which is used by the Result Set interface to search the results returned by the SELECT statement. It provides a set of methods for extracting information from different columns contained in the cursor.
Result Set Metadata: This interface provides information about a returned result set. It is created from a ResultSet object and provides information specific to that object. It provides the information about the number of columns in the result set such as names, and types of the column.
Statement Interface: This is created from the Connection object. It is used to execute standard SQL statements and stored procedures. It provides two main methods, executeQuery() and executeUpdate(). These methods support execution of SQL queries and SQL updates. The executeQuery() method returns a ResultSet object. JDBC API Objects Java provides various objects that can be used in Java applications. These objects provide Java with some of the database specific data types available in most databases.
The table below describes various JDBC API objects:
| Object | Detail |
| Date | It provides an object that can accept database date values. |
| Driver Manager | It provides another way to make a connection to the database. |
| Driver Property Info | It is used to manage Driver objects. |
| Time | It provides an object that can accept database time values. |
| Timestamp | It is used to get the values from the database that are of timestamp data type. |
| Types | It provides a list of predefined integer values that identify the various data types that can be used in JDBC. |
JDBC Exceptions
Whenever an error occurs in Java, an exception is thrown. The JDBC API introduces three new exceptions. These exceptions are discussed as follows:
DataTruncation Exception: This exception is thrown when JDBC unintentionally truncates a data value. The exception provides methods to get information about the data value that was truncated and the truncation error as well.
SQLException Exception: This is thrown by almost all the methods in the JDBC API. It provides methods for getting information about the error and the present state of the SQL transaction.
SQLWarning Exception: This exception is generated when the database issues a warning. The warnings are silently sent to the object whose method caused it to be reported.
JDBC Vs CGI
Before the introduction of JDBC, the Java applications used to call and access CGI (Common Gateway Interface) programs through streams in Java. The CGI scripts in Java call a separate program that provides database access and returns results. The CGI approach is slow and allows bugs to get into the applications. In addition to this, one must know both the technologies - Java and CGI - to make applications, whereas to access the database through JDBC, one must be a master in Java only.
Another strong reason to use JDBC is that it provides faster access than the CGI approach. In CGI approach, another program is called that accesses the database, processes the data, and returns the result back to the calling program in a stream. This requires multiple levels of processing that increase wait time and also allow more bugs to creep into the applications. The figure below demonstrates the way CGI accesses the database. 
When a CGI script is called, a new script is executed through a Web server, whereas execution of a JDBC statement against the database requires only some sort of server that passes the SQL commands through to the database. This increases the speed of execution of SQL statements. The CGI script first connects to the database and processes the results, whereas the JDBC allows the connection of the database to Java applications so that it can perform all the processing.
The figure below demonstrates how a JDBC statement is executed:
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Simulation test and Citrix and 1Y0-256 and CCA and CCEA
Free Practice Test for Citrix Exam 1Y0-256 from Pass4sure.com.
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Here is a free online practice test for exam 1Y0-256 (Citrix Meta Frame Presentation Server 4.0 Administration) at Pass4sure.com Website. This is a mandatory exam to obtain the CCA (Citrix Certified Administrator), CCEA (Citrix Certified Enterprise Administrator) and CCIA (Citrix Certified Integration Architect) certifications.
This exam measures your competency in installing and managing the Server architectural, printing and policies, and enabling Web access and securing published applications and content. There are 10 free questions available in the practice test for exam 1Y0-256 at the Web site.
The practice test comes with 2 modes of testing namely virtual exam and practice exam. Each test mode is supplemented with correct answer explanations that will help you to understand the concepts and clarify your doubts. A review option and a scorecard is also available at the end of the test.
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Simulation test and Cisco Systems and 642-353 and CSNDS
Pass4sure offers free Practice Test for Cisco Exam 642-353
Check out the free practice test for Cisco Storage Networking Design Specialist Exam 642-353 offered by Pass4sure.com. The practice test for exam 642-353 measures your skills in selecting and integrating various Cisco storage products that helps to implement highly scalable, proficient, and high performing storage networking solution.
The practice test comes with 10 free questions and having an option to choose the testing modes i.e., virtual exam and practice exam. Each test mode is supplemented with correct answer explanations that will help you clear your doubts. A review option and a scorecard are also available at the end of the test.
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Sun Education and Study guide and 310-055 and SCJP 5.0
Free Study Guide for SCJP 5.0 Exam CX310-055 from Xyzws.com
Xyzws.com offers free study guide for SCJP 5.0 (Sun Certified Java Programmer 5) Exam CX310-055. This is an entry –level exam essential to qualify various Sun certifications such as Sun Certified Developer for the Java 2 Platform (SCJD), Sun Certified Web Component Developer for the J2EE Platform (SCWCD) certifications and also to certify as the Master CIW Enterprise Developer.
The study guide at the website is divided in to 7 sections containing different topics such as Declarations, Initialization and Scoping, Flow Control, API Contents, Thread, OO Concepts, Collections / Generics, and Fundamentals.
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Oracle and 1Z0-042 and OCA and Article
Automatic Storage Management in Oracle
uCertify offers this free article for Oracle Database 10g: Administration-I that will assist you in your preparation for Exam 1Z0-042 . This exam is required to be certified as OCA Professional. It evaluates your skill of installation, management and maintenance of Oracle10g databases.
Automatic Storage Management
Enterprises are preferably switching from old existing Oracle versions, such as Oracle 8i and Oracle 9i, to Oracle 10g to have various additional profitable features. They often employ the Automatic Storage Management (ASM) option to enhance the manageability and consolidation of a database.
Oracle 10g
Oracle 10g is a revolutionary product in Oracle’s grid computing world. Oracle 10g is a DBMS, which can automate many database tasks. Oracle 10g follows the Oracle’s 9i platform; the letter ‘g’ in Oracle 10g signifies grid computing.
Oracle 10g delivers numerous interesting and dynamic new features. In this article, Automatic Storage Management (ASM) is explained in detail. There are many features available in Oracle 10g that help manage database operations more efficiently. One of the pivotal features of Oracle 10g is Automatic Storage Management (ASM). It is one of the storage options available in Oracle 10g.
Basic Functions of ASM
ASM relieves the burden of disk and storage management by defining the disk groups for file management, as a result of which file groups are reduced, and the time of the DBA is saved.
Note: The main function of ASM is to simplify and automate the database to manage Oracle database files. The RAC helps in automating the database management.
RAC
RAC stands for Real Application Cluster, which is a component provided by Oracle in its 9i version and which is now also available in the 10g version. RAC enables a database to be installed across multiple servers.
The image below depicts a window in which the configuration settings of Automatic Storage Management are detailed. A candidate has to enter the disk group name, the level of mirroring/redundancy, and the requisite data that the cursor therein prompts for. Click the Next button to proceed further.
This article will mainly focus on the following:
- ASM overview
- New features in ASM
ASM Overview
ASM is a very dynamic feature of Oracle 10g, which provides a grouped file system with no further investment on the software.
With ASM, there is no need of enhancing the storage resources for database management. ASM’s intelligent mirroring technology enables triple data protection. It is known as triple data protection because while configuring Automatic Storage Management, a user is provided three levels of redundancy, which are as follows:
- High
- Normal
- External
New Features in ASM
Following are the main new features of ASM:
- ASM can support multiple database versions.
- ASM enhances the manageability of the database.
ASM helps the DBA save money by optimizing storage utilization.
Oracle’s 10g version has enhanced the ASM functionality in the clustered environment, allowing one ASM instance per client to manage all database instances in the cluster, which has removed the requirement of maintaining more than one ASM instance to manage individual database instances.
For higher availability and manageability, ASM’s instance should be installed in a separate ORACLE_HOME parameter, which is ASM_HOME.
ASM enhances I/O performance, as the database files are intelligently distributed across the current active devices. While adding more resources, database file distribution is re-balanced, keeping the database up and running.
ASM has mirroring capability to enhance manageability, which means that ASM can keep duplicate copies of data as a backup for recovery purposes.
Note: DBAs should note that ASM is not general-purpose, and will not replace the OS file system because ASM’s file resources are not directly managed by the OS, but rather it is the ASM’s file resources, which are managed by the file management system of the OS.
Preparing hard disk for configuration of ASM
If the DBA is configuring ASM for Windows NT OS, then the following points should be taken into consideration:
- Investigate for enough space on the system’s hard disk.
- Using the disk partitioning utility (DISKPART.EXE) of Windows creates primary disk partitions, deciding the size of each partition.
Following example can give an idea about how to create partitions:
- C:\>Select disk1
- C:\Disk1 selected.
- C:\Create partition primary size = 100
- C:\Partition created.
- C:\Create partition primary size = 100
- C:\Partition created.
……………….
The following image depicts the list of volumes created via the DISKPART.EXE utility in a Windows NT environment.
This article helps in understanding the fundamental functionality of Automatic Storage Management (ASM).
To read more technical articles for Exam 1Z0-042 and other Oracle certification exam such as OCA 10g, OCP 10g, OCA 9i, OCP 9i, etc., please visit http://www.ucertify.com