IBM i Platform
The IBM i platform is a midrange server offering that uses IBM's proprietary IBM i operating system and includes an integrated database engine. The database is called DB2.
The file system, called Integrated File System (IFS), is comprised of and provides an umbrella for several different sub-file systems. The native file system used by IBM i is QSYS.LIB. Each entity in this file system is called an object. Each object has an object type that is signified by a character string starting with the asterisk (*) character. For example, an executable program object is signified by the character string *PGM; a data queue object is signified by the character string *DTAQ.
A library is a special type of object signified by the character string *LIB. Library objects are similar to directories in Windows and UNIX systems. A library is used to group objects of different types together. However, unlike a directory, a library cannot have another library as a child. Objects such as files (tables), programs, and other native System i type objects can exist only inside a library. An object in a library is addressed as <library name>/<object name>.
Each unit of work processed by the IBM i system is called a job. Each job is uniquely identified by a job number assigned by the system when the job is started. Each job also has a library list associated with it. This is similar to the PATH variable on Windows or LD_LIBRARY_PATH variable on UNIX. When an object is not explicitly qualified using a library name, the object is searched in the library list for the job. The first occurrence of the object in the library list is used. A library list is signified by string *LIBL.