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Compression with ZLIB algorithm - Save Commands and APIs



IBM i 7.5 and IBM i 7.4 add another option to Save commands and APIs for Save Files and Optical (including Virtual Optical) that have the data compression parameter. The new ZLIB option produces a smaller result and improves performance over existing options.


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The ZLIB algorithm provides another option for data compression. Test results show it is often faster than previously available algorithms and generally produces a smaller result, though actual results vary, depending on the compressibility of the data. The new algorithm automatically uses the on-chip Nest Accelerator (NX) GZIP when it runs in Power10 compatibility mode on a Power10 processor and is therefore faster and less CPU-intensive than previously available compression options.

For Save, the previously available options for compression were *LOW, *MEDIUM, and *HIGH.  The additional option for IBM i 7.5 and IBM i 7.4 TR 7 is *ZLIB.

There is no change in the Restore processing.  The Restore process automatically determines the compression that was used.

Here is a list of the Save commands that support *ZLIB:

  • SAV
Here is a list of the APIs that support *ZLIB:
  • Save Object List (QSRSAVO)
  • Save Object (QsrSave)
  • Save to Application (QaneSava)
IBM i 7.5 note:  For the System Administrator to perform a save operation with DTACPR(*ZLIB) and specify TGTRLS(*PRV) -or- TGTRLS(V7R4M0), it is necessary to load the IBM i 7.5 PTFs listed at the end of this topic.  Without the IBM i 7.5 PTFs applied, the operation would fail with this message:
  • CPF37A9 - Specified data compression not supported for target release.
For more information about this topic, see the following sections in IBM Documentation:
For more information about performance aspects, see the topic "What are some considerations for use of data compression in IBM i?" in the document IBM i on Power - Performance FAQ.
Required PTFs for this support:
IBM i 7.5:
   - PTF MF70497
   - PTF SI81754
IBM i 7.4:
   - PTF MF70498
   - PTF SI81755
   - PTF SI81756

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Document Information

Modified date:
10 March 2023