Monthly Archives: June 2012

Database Model

Database Model

A database model is a theory or specification describing how a database is structured and used. S

Database systems can be based on different data models or database models respectively. A data model is a collection of concepts and rules for the description of the structure of the database. Structure of the database means the data types, the constraints and the relationships for the description or storage of data respectively.

A database model is the theoretical foundation of a database and fundamentally determines in which manner data can be stored, organized, and manipulated in a database system. It thereby defines the infrastructure offered by a particular database system.

A data model is not just a way of structuring data: it also defines a set of operations that can be performed on the data. The relational model, for example, defines operations such as select (project) and join. Although these operations may not be explicit in a particular query language, they provide the foundation on which a query language is built.

Below given are the common models

Hierarchical model
Network model
Relational model
Entity-relationship
Object-relational model
Flat model
Multivalue model
Dimensional model
EAV Model

PHP

set up subversion

1) Install SVN

sudo apt-get install subversion libapache2-svn

2) Create your repository. Once svn is installed on your host, you can proceed with the repository set up

svnadmin create /svnrepos

3) Create a SVN User

Run the below given command

vi /svnrepos/conf/svnserve.conf

and paste here the below given code in  svnserve.conf

anon-access = none
auth-access = write
password-db = passwd

4)Create a password file:

vi /svnrepos/conf/passwd
# add users in the format : user = password
phpcode = phppass

5)  Import Your Project

svn import /projects/myrailsproject file:///svnrepos/myrailsproject

6) Start the SVN Server as Daemon

svnserve -d

7) Restart apache

sudo /etc/init.d/apache2 restart

PHP

set up svn

1) Install SVN

sudo apt-get install subversion libapache2-svn

2) Create your repository. Once svn is installed on your host, you can proceed with the repository set up

svnadmin create /svnrepos

3) Create a SVN User

Run the below given command

vi /svnrepos/conf/svnserve.conf

and paste here the below given code in  svnserve.conf

anon-access = none
auth-access = write
password-db = passwd

4)Create a password file:

vi /svnrepos/conf/passwd
# add users in the format : user = password
phpcode = phppass

5)  Import Your Project

svn import /projects/myrailsproject file:///svnrepos/myrailsproject

6) Start the SVN Server as Daemon

svnserve -d

7) Restart apache

sudo /etc/init.d/apache2 restart

General

Daemon

In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user. Typically daemon names end with the letter d: for example, syslogd is the daemon that implements the system logging facility and sshd is a daemon that services incoming SSH connections.

In a Unix environment, the parent process of a daemon is often, but not always, the init process. A daemon is usually created by a process forking a child process and then immediately exiting, thus causing init to adopt the child process. In addition, a daemon or the operating system typically must perform other operations, such as dissociating the process from any controlling terminal (tty). Such procedures are often implemented in various convenience routines such as daemon in Unix.

Systems often start daemons at boot time: they often serve the function of responding to network requests, hardware activity, or other programs by performing some task.

General

Copy-Modify-Merge Solution

Subversion, CVS, and many other version control systems use a copy-modify-merge model as an alternative to locking. In this model, each user’s client contacts the project repository and creates a personal working copy—a local reflection of the repository’s files and directories. Users then work simultaneously and independently, modifying their private copies. Finally, the private copies are merged together into a new, final version. The version control system often assists with the merging, but ultimately, a human being is responsible for making it happen correctly.

General

Lock-Modify-Unlock Solution

Many version control systems use a lock-modify-unlock model to address the problem of many authors clobbering each other’s work. In this model, the repository allows only one person to change a file at a time. This exclusivity policy is managed using locks. one must lock the before making any changes to the files so that any other can not access the file .

General

SVN Repository

Subversion is an open source version control system. Using Subversion, you can record the history of source files and documents. It manages files and directories over time. A tree of files is placed into a central repository. The repository is much like an ordinary file server, except that it remembers every change ever made to files and directories.

Subversion is built on a portability layer called APR—the Apache Portable Runtime library.

Subversion is a centralized system for sharing information. At its core is a repository, which is a central store of data. The repository stores information in the form of a filesystem tree—a typical hierarchy of files and directories. Any number of clients connect to the repository, and then read or write to these files. By writing data, a client makes the information available to others; by reading data, the client receives information from other

What makes the Subversion repository special is that it remembers every change ever written to it—every change to every file, and even changes to the directory tree itself, such as the addition, deletion, and rearrangement of files and directories.

General

Subversion

Subversion is an open source version control system. Using Subversion, you can record the history of source files and documents. It manages files and directories over time. A tree of files is placed into a central repository. The repository is much like an ordinary file server, except that it remembers every change ever made to files and directories.

Subversion is built on a portability layer called APR—the Apache Portable Runtime library.

Subversion is a centralized system for sharing information. At its core is a repository, which is a central store of data. The repository stores information in the form of a filesystem tree—a typical hierarchy of files and directories. Any number of clients connect to the repository, and then read or write to these files. By writing data, a client makes the information available to others; by reading data, the client receives information from other

What makes the Subversion repository special is that it remembers every change ever written to it—every change to every file, and even changes to the directory tree itself, such as the addition, deletion, and rearrangement of files and directories.