Database Reference
In-Depth Information
detect an unavailable primary or secondary replica. hey can re-establish the primary or second-
ary replica after a data node failure. In the data center, each data node is monitored by six peers
installed on diferent racks. In case a data node fails, the peers report the problem. A reconigu-
ration process will be performed on those databases that have a replica on the failed data node.
When a primary replica fails, a secondary replica with the least load is selected to be the new
primary replica. When a secondary replica fails, a new secondary replica is created with the pri-
mary replica. he new secondary replica will be built on a data node that has suicient disk space
and CPU capacity. he gateway will immediately attempt to reconnect the newly created replica.
Owing to the replication and efective recovery of the primary replica, Microsoft Windows Azure
SQL Database is able to maintain 99.9% availability even when 15% of the replicas fail.
Windows Azure SQL Database and SQL Server have a lot in common. Both SQL Server and
Windows Azure SQL Database are used to store and manage the relational data. hey can use
Transact-SQL (T-SQL) to create database objects, manage databases, and query information out
of databases. Many database application development tools work on SQL Server as well as on
Windows Azure SQL Database. Similar to SQL Server, Windows Azure SQL Database includes
SQL Server components such as stored procedures, views, multiple indices, joins, aggregation,
and so on. Windows Azure SQL Database is also able to do some of the administration tasks
such as creating logins, users, roles, and so on. hey support data migration tools such as SQL
Server Integration Services (SSIS), the bulk copy utility (BCP.exe), the System.Data.SqlClient,
SqlBulkCopy class, and the scripts that use INSERT statements to load data into the database.
Like SQL Server, Windows Azure SQL Database also provides functionalities for the server side
processing to reduce network traic and improve performance. Both of them can use database
access technologies such as ADO.NET and ODBC. However, the database access technology
OLE DB is not supported by Windows Azure SQL Database.
Unlike SQL Server, Windows Azure SQL Database does not provide the functionalities
that directly access the underlying hardware. As cloud-based data storage, Windows Azure SQL
Database is not able to determine where to place a database ile on a data storage device. he
database iles will be automatically placed by the Windows Azure platform. Windows Azure SQL
Database does not support database replication or backup-related technologies such as Mirror
Server, RESTORE statement, or Attach Database. Windows Azure SQL Database does not sup-
port SQL Server Agent or jobs, and it does not support distributed transactions. To support SQL
Server, a company needs to develop an IT infrastructure, including the network and powerful
computers installed with server operating system and application software. he company also
needs to take care of security and system update. While using Windows Azure SQL Database,
all these things can be done by cloud providers. Windows Azure SQL Database allows database
developers to work in an environment that is similar to that of SQL Server. he developers can
continue to use the skills learned in the development of SQL Server to develop databases on
Windows Azure SQL Database.
When creating a database on Windows Azure SQL Database, a user can specify the name,
edition, and the maximum size of the database. he user can choose one of the two database
editions, the web edition and the business edition. When the web edition is speciied, a database
can have 1 or 5 GB storage space. When the business edition is speciied, a database can have
10, 20, 30, 40, or 50 GB storage space. When the maximum size is reached, the user can only
read, delete, and truncate tables, drop database objects, and rebuild indexes. he activities such
as creating database objects, inserting new data, and executing stored procedures will be pro-
hibited. here is a limit on the number of databases that can be created in Windows Azure SQL
Database. he maximum number of databases that can be created on each Windows Azure SQL
