Compressed objects and storage space

All of the licensed programs and some objects of the IBM® i operating system ship in a compressed form. This requires less storage space on your system. The system decompresses objects according to certain criteria, which could affect the performance of the system.

System jobs (QDCPOBJx, where x is a number) automatically decompress these objects during the installation process if your system has sufficient unused disk storage. If enough storage space is not available, the system decompresses the objects when you use them, which could affect the performance of the system.

The system decompresses objects according to the following criteria:

  • Greater than 750 MB available storage

    The system submits jobs to decompress all system objects just installed.

  • 250-750 MB available storage

    The system automatically decompresses only frequently used objects. Object-usage information (the number of days an object has been used and the last-used date) is used to identify frequently used objects. The system decompresses any object that was used within the last 14 days and which also has been used at least five times. The system leaves the remaining low-use objects in compressed form.

    • This does not include decompression of objects that are shipped in the operating system and in library QSYS. The system resets usage information for those objects during the installation process. For all other licensed programs, the object usage information is kept during the installation process.
    • A call to a system program does not update its usage information; the system does not automatically decompress programs in constrained storage mode. However, high-use programs ship in decompressed form and are not considered able to be compressed.
  • Less than 250 MB available storage

    The system does not submit the decompression jobs and instead decompresses the objects as they are used.

Note: The QDCPOBJx system jobs might run for some time after the installation process completes.