Methods for viewing compression information

You can display compression statistics, information about compression dictionaries, and the compression dictionary.

The following table describes the different methods that you can use to view compression information.

Table 1. Methods to view compression information
Method Description
oncheck -pT or oncheck -pt command Displays statistics on any compressed items in the "Compressed Data Summary" section of the output. If no items are compressed, the "Compressed Data Summary" section does not appear in the output.

For example, for row data, oncheck -pT displays the number of any compressed rows in a table or table fragment and the percentage of table or table-fragment rows that are compressed.

onlog -c option Uses the compression dictionary to expand compressed data and display the uncompressed contents of compressed log records.
onstat –g dsk option Displays information about the progress of currently running compression operations.
onstat -g ppd option Displays information about the active compression dictionaries that exist for currently open compressed fragments (also referred to as partitions). This option shows the same information as the syscompdicts view in the sysmaster database.
syscompdicts_full table in the sysmaster database Displays metadata about the compression dictionary and the compression dictionary binary object.

Only user informix can access this table.

syscompdicts view in the sysmaster database Displays the same information as the syscompdicts_full table, except that for security reasons, it excludes the dict_dictionary column, which contains the compression dictionary binary object.
UNLOAD TO 'compression_dictionary_file' SELECT * FROM sysmaster:syscompdicts_full; SQL statement View the compression dictionary in a file.

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