IBM SG24-6526-00 manual The iSeries integrated file system

6.1 The iSeries integrated file system

Several releases ago, IBM reorganized considerably the file system of the iSeries server. A new UNIX- or Windows NT-like file system called the integrated file system (IFS) was introduced. The original file system, for example QSYS, other libraries, and their contents became part of this new system.

Files in new areas of the IFS are quite different than the familiar database files of the iSeries. They do not have fixed length records. In fact, they do not have a structure known to the operating system. They are simply stored bytes. The data may be readable text in ASCII, EBCDIC or Unicode. It could be Java byte code, PC executable code, or many other types. Some may be suitable for viewing and others may not be. You need to know which programs are intended to read and write these files. The extension (the portion of the name after the dot) often suggests the nature of the contents but it is not exact. A file whose name ends in

.java may be Java source code, but it could be anything.

When necessary, these files are called stream files to distinguish them from database files. They are also commonly called IFS files. To a UNIX or Windows NT user, they are simply files even if they contain executable program code.

WebSphere and its applications make considerable use of stream files. Java source and byte code is stored in stream files. The source code is in ASCII, and the byte code is not humanly readable. Configuration and log files used by these applications are typically stream files, which are usually ASCII, but may be EBCDIC.

Many experienced iSeries users are not familiar with these stream files, so we added a number of topics that deal with them in this section.

The IFS is similar to UNIX, except that in general, file names are not case sensitive. The system remembers the case that is used when the file is created, but it can be addressed later using a different case. Although this is not always true, we recommend that you use consistent case. (Some UNIX knowledge will be valuable for installing and managing a WebSphere application.) The IFS even supports links, both hard and soft, but they are not used by System21 applications.

The IFS is similar to the file system of Windows NT, but less so than UNIX. Here are some significant differences from Windows NT:

￿Although the iSeries has disk drives, they are not reflected in file naming so there is no C: drive, D: drive, etc.

￿The directory separator is / rather than \.

￿The root directory is called /, not C:\. All iSeries storage is somewhere within this directory.

One aspect in which the IFS is more like Windows NT than UNIX is regard to case. Outside the special directory QOpenSys (see the following list), file names are not case sensitive. For example, FRED, Fred, and fred all refer to the same file. Like Windows NT, the IFS remembers the case but allows access through names with different cases.

Certain top-level directories have special properties, which include:

￿QDLS: The old folder / document file system. This exists only for compatibility. This is not used by System21 applications and we do not recommend using it.

￿QOpenSys: Within this directory, names are case sensitive. This is intended for porting UNIX applications. It is not used by System21 applications.

￿QOpt: Optical storage, such as CD drives. This is used during WebSphere installation.

138Geac System21 commerce.connect: Implementation on the iSeries Server