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Upgrading existing attachments from Huffman to LZ1 compression

Technote (FAQ)


Question

You configure a Lotus Domino® database to use LZ1 compression and want to convert existing attachments to this algorithm to take advantage of its superior compression ratio. How can you upgrade the compression algorithm for existing attachments?

Answer

The enhancement SPR# ASCR667FLH introduced additional functionality to the Compact task in Domino 6.5.6 and 7.0.1 that allows you to convert existing compressed attachments to either Huffman or LZ1 compression. The switch, -ZU, converts all compressed attachments to LZ1. The switch, -ZD, converts all compressed attachments to Huffman. The feature does not act on attachments that were not previously compressed and does not exist in Notes' Compact code.
In order for the -ZU switch to work, the database property, "Use LZ1 compression for attachments", must be enabled. If the property is not enabled, then the -ZU switch has no effect. The -ZD switch converts to Huffman regardless of the property setting.

For Domino 6.5.6 only, the following notes.ini parameter must be set in order for either switch to operate:

    DEBUG_ENABLE_LZ1_REPAIR=1

The parameter can be set for the current Domino session by issuing the following command at the server console:
    Set Config DEBUG_ENABLE_LZ1_REPAIR=1

  • To convert existing attachments from Huffman to LZ1 compression, perform the following steps:
      1. Make sure 'Use LZ1 compression for attachments' (the default) is enabled. This setting is found in Application Properties --> Advanced (beanie) panel. (These settings, if enabled in the mail or other template, can be set on individual databases by a design refresh.)

      2. From the server console, run the following command (without quotes):
        "load compact -C -ZU"
  • To convert existing attachments from LZ1 to Huffman compression, from the server console, run the following command (without quotes): "load compact -C -ZD"

    NOTE: The conversion to Huffman compression will take place regardless of whether the "Use LZ1 compression for attachments" property is enabled or disabled.

If you fail to use the "-C" parameter for the compact command, then the following warning message appears in the log:
    "01:04:25 PM Informational, to move objects into LZ1 and enable LZ1 you need to perform a copy-style compaction with the -Z tag (-C -ZU ) on discuss.nsf."

Related information

Error: 'Invalid Encoded Data - Attachment May be Corrup
How can you programmatically set the LZ1 compression op
Use LZ1 compression for attachments

Document information

More support for: IBM Domino
Deployment

Software version: 7.0.1, 8.0, 8.5, 9.0, 9.0.1

Operating system(s): AIX, Linux, Solaris, Windows

Software edition: All Editions

Reference #: 1256241

Modified date: 05 February 2010


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