Backup software and recovery software creates copies of files, databases, disks, drives, or entire computer systems to avoid the permanent loss of data. These applications also enable the retrieval of data from damaged files, storage devices, or file systems. There are two types of data backups: physical and logical. Physical backups are full copies of files. Database administrators (DBAs), systems administrators, and other information technology (IT) personnel perform physical backups to copy files from one location to another, such as from a server disk drive to a backup disk. Logical backups contain data that is exported via structured query language (SQL) commands and stored in a binary file. Backup and recovery software for crash recovery, automatic instance recovery, and media failure is also available. Selecting backup software and recovery software requires an understanding of voluming, data storage, data compression, and remote backups. Voluming is a data storage technique that enables backup and recovery applications to compress large amounts of data. Larger blocks may be split into smaller ones for storage purposes, and then reassembled during data recovery. Typically, data backups are housed on removable storage media such as computer disks (CDs) and external hard drives. Data compression reduces the size of the data backups so that less disk space is required. In organizations that perform manual backups, features such as remote backup may be required. Backup and recovery software with remote backup services enable users to save or copy their files to on online system. Remote backup services may be structured to accommodate a client’s specific software configuration, and designed to run according to a schedule. Backup software and recovery software for database administration (DBA) is designed to copy critical database components such as the data files, control files, on-line redo log files, and archived redo log files. Data files are divided into data blocks. The first block of each file is a header that contains information such as the file size, block size, tablespace, and timestamp. Control files contain the operating system (OS) filename as well as the names of other files in the database. On-line redo log files are used to record all changes made to the database. Archived redo log files are redo logs that enable complete data recovery from either instance failure or media failure. Typically, instance failure occurs during a power outage. Backup software and recovery software for protection against media failure is also available.