Type2 IFS Directories
October 23, 2002 Timothy Prickett Morgan
I have heard that the Integrated File System (IFS) has a new structure in V5R2. Do you know anything about this?
With V5R2, IBM introduced a new and improved directory structure for the IFS. The new model is called Type2 and the original directory structure, which until then had no name, was labeled Type1. Type2 is the new standard for IFS directories and directories shipped with future iSeries systems will be in the Type2 format. Type2 directories do not apply to the entire IFS, but to the root, QOpenSys, and user-defined files systems only.
Type2 directories are better than Type1 directories for several reasons. First is performance. Operations against Type2 directories are faster than they are against Type1 directories.
- to create a Type2 directory is up to twelve times faster
- to delete a Type2 directory is up to four times faster
- to read a Type2 directory is up to four times faster
- to open a Type2 directory may be twice as fast
- to run Reclaim Storage (RCLSTG) against a Type2 directory may be twice as fast
Second is reliability. Type2 directories provide better recovery from system crashes and reduce the need for running RCLSTG.
Third is functionality. Type2 directories will support operations that Type1 directories do not have and will never have.
Fourth is size. Type2 directories occupy less room on a disk than Type1 directories. For small directories, the reduction in size is very large. However, for larger directories, the size savings may only be ten percent or so.
Last is capacity. Type2 directories can have up to one million subdirectories.
Type2 directories are also available for V5R1. For more information, see the APAR II13161 Web page .
IBM supplies utilities for V5R1 and V5R2 to convert Type1 directories to Type2 directories. For V5R2, the conversion utility runs from the Convert Directory (CVTDIR) command. The V5R1 conversion utility is part of APAR II13161. You may convert all file systems to the Type2 format at once, but you do not have to. You may convert only the root system, the QOpenSys system, or a user-defined system in an auxiliary storage pool (ASP).
The conversion utility can be used to do the following:
- determine which directory structure a file system uses
- estimate the time and disk space required for the conversion
- convert the directories in a file system
Conversion is a one-way street. The conversion utility will not convert Type2 directories to Type1 format.
For more information, read Jeff Parker’s article, “Get Ready to Boost Your IFS Performance with V5R2“, which was published in August 29, 2002, issue of The Four Hundred.
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