Database Administration

Rehema Baguma

Who is a DBA

• A person responsible for designing, implementing, and maintaining the database system; establishing policies and procedures pertaining to the management, security, maintenance, and use of the database management system.

Skills for a DBA• Communication skills• Knowledge of database theory• Knowledge of database design• Knowledge about the RDBMS e.g. Microsoft SQL Server• Knowledge of Structured Query Language (SQL)• General understanding of distributed computing architectures

e.g. Client/Server, Internet/Intranet, Enterprise• General understanding of the underlying operating system,

e.g. Windows, Linux• General understanding of storage technologies, memory

management, disk arrays

Roles of a DBA• Installing and upgrading the database server and application tools• Allocating system storage and planning future storage requirements for the

database system• Modifying the database structure, as necessary, from information given by

application developers verbally• Enrolling users and maintaining system security• Ensuring compliance with database vendor license agreement• Controlling and monitoring user access to the database• Monitoring and optimizing the performance of the database• Planning for backup and recovery of database information• Maintaining archived data• Backing up and restoring databases• Contacting database vendor for technical support• Generating various reports by querying from database as per need

Understanding the DBMS Architecture

• The database architecture is the set of specifications, rules, and processes that dictate how data is stored in a database and how data is accessed by components of a system. – It describes the organization of all database objects and

how they work together. – It affects integrity, reliability, scalability, and performance.

Data Model

• Data model:   Collection of concepts that describe the structure of a database• Provides means to achieve data abstraction• Suppression of details of data organization & storage

Categories of Data Models– High-level or conceptual data models: close to the way

many users perceive data– Low-level or physical data models: Describe the

details of how data is stored on computer storage media

OR

• External; How data is viewed by an individual user• Conceptual: How data is viewed by a community of users• Internal: How data is physically stored

Categories of Data Models!

Categories of Data Models cont..

Entity•Represents a real-world object or concept e.g. studentAttribute•Represents some property of interest e.g. year of study•Further describes an entity•Relationship among two or more entities•Represents an association among the entities•Entity-Relationship model•Relational data model

– Based on relation/table principle for data storage and management

Categories of Data Models cont..• Object data model

– New family of higher-level implementation data models– Closer to conceptual data models

• Physical data models– Describe how data is stored as files in the computer

• Access path– Structure that makes the search for particular database records

efficient

• Index– Example of an access path– Allows direct access to data using an index term or a keyword

Schemas instances and database State• Database schema

– Description of a database

•  Schema diagram• Displays selected aspects of schema•  Schema construct

– Each object in the schema

•  Database state or snapshot– Data in database at a particular moment in time

•  Initial state– Populated or loaded with the initial data

• Valid state– Satisfies the structure and constraints specified in the

schema

Example of a Database Schema

!

DBMS Interfaces

Menu-based interfaces for Web clients or browsing  Forms-based interfaces•Graphical user interfaces  Natural language interfaces•Speech input and output

 

Database Components

• Buffer management• Stored data manager• DDL compiler

– DDL compiler is the compiler whose job is to convert high level commands to low level commands..

• Interactive query interface• Query compiler• Runtime database processor• System catalog• Concurrency control system• Backup and recovery system

DB system Utilities• Loading

– Load existing data files

•  Backup– Creates a backup copy of the database

• Database storage reorganization– Reorganize a set of database files into different file

organizations

• Performance monitoring– Monitors database usage and provides statistics to the DBA

Centralised Vs Client server DB architectures

• Centralized DBMSs Architecture– All DBMS functionality, application program execution, and

user interface processing carried out on one machine

• Servers with specific functionalities– File server

– Maintains the files of the client machines.

• Printer server– Connected to various printers; all print requests bythe clients are forwarded to this machine

• Web servers or e-mail servers

Two Tier, Three Tier and N-Tier• Server handles

– Query and transaction functionality related to SQL processing

• Client handles– User interface programs and application programs– Open Database Connectivity (ODBC)–   Provides application programming interface (API)– Allows client-side programs to call the DBMS

• Both client and server machines must have the necessary software installed

•   Three Tier & N-Tier• Application server or Web server

– Adds intermediate layer between client and the database server: Runs application programs and stores business rules

Two Tier, Three Tier and N-Tier

• N-tier– Divides the layers between the user and the stored data further

into finer components

Understanding and using the system log for DB admin tasks

• DBMS e.g. MySQL Server has several logs that can help you find out what activity is taking place.

• By default, no logs are enabled (except the error log on Windows).

• By default, the server writes files for all enabled logs in the data directory.

• You can force the server to close and reopen the log files (or in some cases switch to a new log file) by flushing the logs– Using a FLUSH LOGS statement

• The binary log is flushed when its size reaches the value of the max_binlog_size system variable.

• You can enable or disable logging, or change the log file name.

Understanding and using the system log in database admin cont..

DBMS e.g. MySQL Server has several logs that can help

Log Type Information Written to Log

Error logProblems encountered starting, running, or stopping DBMS

General query logEstablished client connections and statements received from clients

Binary log Statements that change data (also used for replication)

Relay log Data changes received from a replication master server

Slow query logQueries that took more than the established thresh hold (long query time) to execute

Database Tuning

• What is database tuning, and how can it be achieved in database administration?

Database backup and recovery• If you're storing anything in databases that you do not want to

lose, it is very important to make regular backups of your data to protect it from loss

• There are two easy ways to backup and restore the data in MySQL database.– Back up from the Command Line (using mysqldump)– Back up with Compress

Back up From the Command Line (using mysqldump)

• You can backup MySQL data using the mysqldump command.– This command connects to the MySQL server and creates an SQL

dump file.

• The dump file contains the SQL statements necessary to re-create the database. The syntax is : – mysqldump --opt -u [uname] -p[pass] [dbname] > [backupfile.sql]

• [uname] Your database username • [pass] The password for your database (note there is no space between -p and the

password) • [dbname] The name of your database • [backupfile.sql] The filename for your database backup • [--opt] The mysqldump option

BBack up from the Command Line (using mysqldump)

• E.g. mysqldump -u root -p Tutorials > tut_backup.sql– Backs up database named 'Tutorials' with the username 'root' and with

no password to a file tut_backup.sql

• You can also choose to specify certain tables of the database you want to backup by separating each table name with space.– mysqldump -u root -p Tutorials php_tutorials asp_tutorials >

tut_backup.sql

• You can back up more than one database at once using the --database option followed by the list of databases you would like to backup separated by space.– mysqldump -u root -p --databases Tutorials Articles Comments >

content_backup.sql

Back up From the Command Line (using mysqldump)

• To back up all the databases in the server at once you use the --all-databases option. mysqldump -u root -p --all-databases > alldb_backup.sql

• The mysqldump command has also some other useful options:–--add-drop-table: Tells MySQL to add a DROP TABLE statement before each CREATE TABLE in the dump.–--no-data: Dumps only the database structure, not the contents. –--add-locks: Adds the LOCK TABLES statement you can see in the dump file.

Backing up MySQL Database with Compress

• If your mysql database is very big, you might want to compress the output of mysqldump. – pipe the output to gzip to get the output as gzip file.

• mysqldump -u [uname] -p[pass] [dbname] | gzip -9 > [backupfile.sql.gz]

• To extract the .gz file, use the command below:– gunzip [backupfile.sql.gz]

Restoring MySQL Database

• To re-create the Tutorials database follow two steps:– Create an appropriately named database on the target machine

– Load the file using the mysql command:• mysql -u [uname] -p[pass] [db_to_restore] <

[backupfile.sql] e.g.• mysql -u root -p Tutorials < tut_backup.sql

• To restore compressed backup files, do the following:• gunzip < [backupfile.sql.gz] | mysql -u [uname] -p[pass]

[dbname]• To restore a database that already exists, you'll need to use

mysql import command as follows: mysqlimport -u [uname] -p[pass] [dbname] [backupfile.sql]

Backing Up and Restoring using PHPMyAdmin

• To backup MySQL database using PHPMyAdmin, just follow a couple of steps using phpMyAdmin’s menu options:– Open phpMyAdmin. – Select your database by clicking the database name in the list on the

left of the screen. – Click the Export link. This should bring up a new screen that says View

dump of database (or something similar). – In the Export area, click the Select All link to choose all of the tables in

your database. – In the SQL options area, click the right options. – Click on the Save as file option and the corresponding compression

option and then click the 'Go' button. A dialog box should appear prompting you to save the file locally.

Restoring your database using phpMyAdmin– Open phpMyAdmin. – Create an appropriately named database and select it by

clicking the database name in the list on the left of the screen. • If you would like to rewrite the backup over an existing database then

click on the database name, select all the check boxes next to the table names and select Drop to delete all existing tables in the database.

– Click the SQL link. This should bring up a new screen where you can either type in SQL commands, or upload your SQL file.

– Use the browse button to find the database file. – Click Go button. This will upload the backup, execute the SQL

commands and re-create your database.

Securing your Databases• General factors that affect security.

– choosing good passwords, not granting unnecessary privileges to users, ensuring application security by preventing SQL injections and data corruption, etc.

• Security of the installation itself. – The data files, log files, and the all the application files of your

installation should be protected to ensure that they are not readable or writable by unauthorized parties e.g. not storing them in the default directory.

• Access control and security within the database system itself,– Grant users only required access to the databases, views and stored

programs in use within the database.

• Network security of MySQL and system. – Ensure appropriate permissions for users, an up-to-date anti virus,

firewalls, ensure other Network security measures• Adequate & appropriate backups & tested recovery solution. See

http://dev.mysql.com/doc/refman/5.5/en/security.html

Using an example of an organisation of your choice, list and explain best practices for database management-feedback from group discussion.

•Replication in different locations•Normalised tables•Vendor specification guidelines•Backup & recovery plan/schedule•Configure audit logs/moninotring usage•Protect sensitive data e.g. encryption of passwords & credit card information•Database documentation that provides a clear understanding of the DB•Secure default configurations•Applying software updates for the DBMS & other applications

• DB & web server must be placed in different machines for better security & performance

• Routine check of DB & log size• Appropriate management of user access privileges• Run frequently penetration & intrusion detection tests

Develop & execute good database management practices

After people, data is your most important asset: below are some best practices for good DB management•Left unattended, databases will turn into piles of mush.

– develop data entry policies and procedures, and train everyone who enters data.

•Have some one in charge of training, user support, and data quality . – At a small organization, this might be a small part of someone's job. At a

large organization, it might need to be a whole department.

•Run backups religiously. Do test them periodically to make sure you can recover data.•Keep a copy of your data off-site e.g.

– online backup service, a vendor that provides offsite storage and retrieval, or even by sending a backup home with a staff member but be aware about risks like theft, loss, aunauthorised access, etc.

Develop & execute good database management practices

• Do all you can to prevent staff from downloading sensitive data (S.S numbers or credit card data) to laptops or memory sticks. – Use encryption on laptops and memory sticks. – Tools like Identity Finder, Proventsure, SENF, and Spider will scan your

computers for sensitive data.• Require strong passwords. Do not share passwords. Change

passwords regularly.• Monitor your data entry.

– Run reports that look for common errors. – Identify staff members who repeatedly make errors and provide

additional training. – If the errors continue, take away their data entry permissions.

Develop & execute good database management practices

• Run your database on a need-to-know basis. – Give staff and volunteers access to only the data they need to see or

change to do their jobs -- but make sure that they do have access to the data they need.

• Make sure your database has enough security options.– provide read-only access where rights are not necessary e.g. names

and addresses but not gifts. – provide update access to only certain portions of your data, like

updating addresses but not entering gifts. – restrict access to sensitive functions like posting a gift batch – restrict the ability to run mass updates or delete records.

See more at: http://www.rlweiner.com/best-practices-for-managing-a-database#sthash.K8GPelsu.dpuf

• See also PDF about best practices for database management

Individual AssignmentUsing an example and a case study of either a bank, hospital or a university, a)State and explain 5 best practices for:

i. Effective web designii. Effective web administrationiii. Effective database administration (20 marks)

b)Develop a web based application using the practices given in (a) (20marks)