uCertify Articles » 70-547-CSHARP http://www.ucertify.com/article Just another WordPress weblog Wed, 04 Nov 2009 00:00:00 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 Database Transaction and Security http://www.ucertify.com/article/database-transaction-and-security-2.html http://www.ucertify.com/article/database-transaction-and-security-2.html#comments Fri, 25 Sep 2009 00:00:00 +0000 uCertify 3501075

First of all, we need to understand what is a transaction in a database? and how does it affect the database?

A transaction is a group of actions such as insert, update, and delete performed on the database to change the state of a database. After a transaction is performed successfully, the database changes to a new state from its existing state.

The databases that support transaction are known as transactional databases. Most of the modern day relational databases support transaction.

A single transaction may require many SQL queries to execute to change the current state of the database. It is also important that all the queries be executed. For example, if money is transferred from one account to another, then in this scenario, the account from which the money is taken out should be debited and the account to which the money is deposited should be credited.

A transaction is issued to the database using SQL (structured query language) and has the following stages:

  • A transaction begins.
  • Execution of queries to change the current state of the database.
  • After the successful execution of all the queries, a transaction is committed, i.e. the changes are saved permanently.

A database transaction has the following properties:

  • Atomicity
  • Consistency
  • Isolation
  • Durability

Each of these properties is discussed below:

Atomicity: This property suggests that either all the changes are made in the database or no change has been made. It ensures that either a transaction is committed (i.e. all the changes made to the database are permanently saved) or rolled back (i.e. no change has been made and the database is recovered to its original state).

Consistency: This property suggests that the database remains in a valid state before and after the transaction is committed. This means that a transaction cannot violate the business rules or integrity constraints of the database. If an integrity constraint states that an account cannot be debited if the balance is less than $500, then any transaction violating this rule will be aborted.

Isolation: This property ensures that a transaction is isolated from any outside operation. This means that data in a transaction cannot be viewed in its intermediate state.

Durability: This property refers that once the user has been notified about the success of the transaction, the transaction will continue and not revert back. This implies that the transaction is being checked for all data integrity constraints and no constraint has been found violated.

Transaction Logs:

A majority of relational databases that we use provide support for transaction logging. Transaction logging is a process in which each transaction committed against the database is logged and the original value of the data is stored. When a SQL query gets executed to change the values in the database, then the original data values are stored in the transaction log. These values are stored so that the database can be recreated using these values in case a transaction fails. A transaction log keeps on storing the original data values until a transaction is committed or rolled back.

Another important aspect of transaction processing is locking. For example, if a user begins a transaction and performs an action that causes to lock a certain portion of the database, then no other user is allowed to access the locked data until the transaction is completed.

Database Security:

The database security is of great importance and a major concern for any organization. Securing the data from people of malicious intent, accidental damage, catastrophic damage is a great challenge for a Database Administrator. The Database Administrator decides the level of security keeping in view the sensitivity of data. There are different levels of security.

At the lowest level of security, there is no restriction, i.e. everybody has full access to the database. This level of security is implemented where there is already network security through which access can be restricted. In such type of scenario, there is no need to duplicate the security scheme.

The next level of security is share level security. At this level, the Database Administrator assigns a password to the whole database and the users who know the password can access the full database. This level of security is easy to implement and administer because it requires to change only one password periodically. This type of security is adequate in situations where the organization wants to provide full access to the database to its employees. For example, a database that stores annual holiday list or database regarding news, which the organization publish from time to time.

After this level comes user level security. At this level, each user is assigned some particular privileges by the Database Administrator. For example, it is the prerogative of the Database Administrator to assign different rights to different users so that each user can be restricted to use the database. He can assign various rights such as some users are entitled to only view the data, some can modify by adding or deleting entries from the database, etc. This level of security is a bit difficult to implement and administer, but it provides a higher degree of security to the data. This level of security can be implemented on individual users as well as a group of users. To implement on a group of users, each group should be identified first such as system administrators, order-entry clerks, salespeople, and so forth-and then determine the security privileges that each role has for each object in the system.

Auditing:

In addition, in order to restrict the access of the database, the Administrator might want to track the details about what the users have done on the database or who logged on to the database, etc. The requirement of keeping such audit trails varies from organization to organization. Suppose the Database Administrator might want to keep the details about who logged and logged off, then a single entity with the attributes UserName , LogOn , and LogOff will probably suffice the purpose.

Keeping track of deletions can be more complex. The Database Administrator has a couple of options here. He can prevent users from actually deleting records at all and set a Deleted flag instead. This is a useful technique if he wants to copy the records to an archive file before removing them from the database.

After modeling the audit requirements, the Database Administrator needs to restrict access to the audit tables.

Share/Bookmark]]> http://www.ucertify.com/article/database-transaction-and-security-2.html/feed 0 What is the ToolStrip control? http://www.ucertify.com/article/what-is-the-toolstrip-control.html http://www.ucertify.com/article/what-is-the-toolstrip-control.html#comments Wed, 02 Sep 2009 00:00:00 +0000 uCertify 5401007

The ToolStrip control is a special control that is used to create professional looking and highly optimized toolbars, status bars, and menus in a Windows form. It can host ToolStripItem controls, which are similar to common controls such as Button, Label, and ComboBox. However, ToolStripItem controls are specifically designed to be hosted in the ToolStrip control.

Share/Bookmark]]> http://www.ucertify.com/article/what-is-the-toolstrip-control.html/feed 0 What is Web Setup project? http://www.ucertify.com/article/what-is-web-setup-project-2.html http://www.ucertify.com/article/what-is-web-setup-project-2.html#comments Tue, 01 Sep 2009 00:00:00 +0000 uCertify 1501180

The Web Setup project is a Setup and Deployment project, which is used to create installation packages for the deployment of Web-based applications such as XML Web services, Web applications etc., to a Web server. It creates an (.msi) installer package. Using the Web Setup project for deployment handles the registration and configuration issues automatically.

Note: The Web Setup project installs files into the virtual directory on a Web server.

Share/Bookmark]]> http://www.ucertify.com/article/what-is-web-setup-project-2.html/feed 0 What is Sn.exe? http://www.ucertify.com/article/what-is-snexe-2.html http://www.ucertify.com/article/what-is-snexe-2.html#comments Mon, 31 Aug 2009 00:00:00 +0000 uCertify 1501041

Strong Name (Sn.exe) is a tool used to sign assemblies with strong names. It also provides signature generation, signature verification, and key management. Following is the syntax for using Sn.exe:

sn [options [parameters]]

where, the term options specifies the options to be used, and parameters specifies the parameters used with options. Following are the options that are commonly used with Sn.exe:

Option Description
-k It is used to generate a new key pair and write it to a specified file.
-i It is used to install a key pair from a specified key container that resides in a strong name Cryptographic Service Provider (CSP).
-p It is used to extract a public key from a key pair file and store it in another key pair file.
-v It is used to verify the strong name in an assembly.
-d It is used to delete a specified key container from the strong name CSP.
-D It is used to verify that two assemblies differ only by signature.
-Vx It is used to remove all verification-skipping entries.
Share/Bookmark]]> http://www.ucertify.com/article/what-is-snexe-2.html/feed 0 What is Regsvcs.exe? http://www.ucertify.com/article/what-is-regsvcsexe-2.html http://www.ucertify.com/article/what-is-regsvcsexe-2.html#comments Mon, 31 Aug 2009 00:00:00 +0000 uCertify 1501136

.NET Services Installation (Regsvcs.exe) is a tool used to load and register assemblies as well as generate, register, and install a type library into a COM+ 1.0 application. It is also used to configure services that are programmatically added to a class.

Share/Bookmark]]> http://www.ucertify.com/article/what-is-regsvcsexe-2.html/feed 0 What are the disadvantages of using profile properties server-based technique? http://www.ucertify.com/article/what-are-the-disadvantages-of-using-profile-properties-server-based-technique.html http://www.ucertify.com/article/what-are-the-disadvantages-of-using-profile-properties-server-based-technique.html#comments Tue, 18 Aug 2009 00:00:00 +0000 uCertify 5608099

The following are the disadvantages of using profile properties :

  • The profile data is stored in a data store, instead in a memory. Therefore, the performance of profile properties becomes slow in comparison with using a session state technique.

  • A profile provider should be configured for using profile properties. However, all the other profile properties that need to be stored in a data store also required to be pre-configured.

  • Profile properties require a certain amount of maintenance, as profile data is persisted to a non-volatile storage. Each application should call the appropriate cleanup mechanisms provided by the profile provider when the data becomes useless.
Share/Bookmark]]> http://www.ucertify.com/article/what-are-the-disadvantages-of-using-profile-properties-server-based-technique.html/feed 0 What are the different usages of server-based state management techniques? http://www.ucertify.com/article/what-are-the-different-usages-of-server-based-state-management-techniques.html http://www.ucertify.com/article/what-are-the-different-usages-of-server-based-state-management-techniques.html#comments Tue, 18 Aug 2009 00:00:00 +0000 uCertify 5608100

The following table describes the different usages of server-based state management techniques:

State Management Techniques Usages
Session State It is used when small amounts of state management information that is specific to an individual session need to be stored for each user session. It is also used when there is no security issue.
Application State It is used when infrequently changed global information that is used by many users needs to be stored. It is also used when there is no security issue.
Profile Properties It is used when a user-specific information that needs to be persisted even after the user session has been expired. The data can be retrieved again on subsequent visits to an application.
Database Support It is used when large amount of information needs to be stored in a data store. It is used to manage transactions of a user. However, there can be a security issue.
Share/Bookmark]]> http://www.ucertify.com/article/what-are-the-different-usages-of-server-based-state-management-techniques.html/feed 0 What are the advantages of using a database for storing server-based state management information? http://www.ucertify.com/article/what-are-the-advantages-of-using-a-database-for-storing-server-based-state-management-information.html http://www.ucertify.com/article/what-are-the-advantages-of-using-a-database-for-storing-server-based-state-management-information.html#comments Tue, 18 Aug 2009 00:00:00 +0000 uCertify 5608101

The following are the advantages of using a database for storing server-based state management information:

  • Large amount of information can be stored in a database.

  • To access a database, authentication and authorization is required for security purpose.

  • Information in a database can be stored without any time limit. The amount of information is not subjected to the availability of a Web server.

  • A database provides facilities such as triggers, referential integrity, and transactions to maintain valuable data.

  • The information that is stored in a database is accessible to a wide variety of information-processing tools.

  • A wide variety of custom configurations and database tools are available for managing valuable information for a Web server.
Share/Bookmark]]> http://www.ucertify.com/article/what-are-the-advantages-of-using-a-database-for-storing-server-based-state-management-information.html/feed 0 What are the disadvantages of using a database to store server-based state management information? http://www.ucertify.com/article/what-are-the-disadvantages-of-using-a-database-to-store-server-based-state-management-information.html http://www.ucertify.com/article/what-are-the-disadvantages-of-using-a-database-to-store-server-based-state-management-information.html#comments Tue, 18 Aug 2009 00:00:00 +0000 uCertify 5608102

The following are the disadvantages of using a database to store server-based state management information:

  • The hardware and software configurations can become more complex if state management information is stored in a database.

  • A poorly constructed relational data model for a database, can lead to scalability issues.

  • Too many queries in a database can adversely affect the performance of a Web server.
Share/Bookmark]]> http://www.ucertify.com/article/what-are-the-disadvantages-of-using-a-database-to-store-server-based-state-management-information.html/feed 0 What are the advantages of using session state server-based technique? http://www.ucertify.com/article/what-are-the-advantages-of-using-session-state-server-based-technique.html http://www.ucertify.com/article/what-are-the-advantages-of-using-session-state-server-based-technique.html#comments Mon, 17 Aug 2009 00:00:00 +0000 uCertify 5608097

The following are the advantages of using session state server-based technique:

  • It is easy to use and is familiar to ASP.NET developers. It is also consistent with other .NET Framework classes.

  • Several session management events can be raised and can be used by Web-based applications.

  • The session state data variables are preserved even if the IIS and the worker-process is restarted without losing any session data. Therefore, the data is stored in another process space of a Web application.

  • The session data can be persisted among multiple application processes such as a process in a Web farm or a Web garden.

  • It can be used both in multi-computer and multi-process configurations. Therefore, it optimizes scalability of a Web application.

  • It is used without the support of cookies. Therefore, it requires a session identifier to be placed in a query string.

  • It can be customized and extended by writing a custom session-state provider. It can then be stored in a custom data format in a data storage mechanism such as a database, an XML file, or a Web service.

However, session state has a drawback. The state management information stays in memory as long as a session is alive. Therefore, it degrades the performance of a Web server. The data variables that contain blocks of information such as large datasets can also affect the performance of a Web server, as server load may increase.

Share/Bookmark]]> http://www.ucertify.com/article/what-are-the-advantages-of-using-session-state-server-based-technique.html/feed 0