This parameter indicates the maximum size of the heap used in collecting statistics using the RUNSTATS command.
Recommendation: The default value is appropriate when no distribution statistics are collected or when distribution statistics are only being collected for relatively narrow tables. The minimum value is not recommended when distribution statistics are being gathered, as only tables containing 1 or 2 columns will fit in the heap.
You should adjust this parameter based on the number of columns for which statistics are being collected. Narrow tables, with relatively few columns, require less memory for distribution statistics to be gathered. Wide tables, with many columns, require significantly more memory. If you are gathering distribution statistics for tables which are very wide and require a large statistics heap, you may wish to collect the statistics during a period of low system activity so you do not interfere with the memory requirements of other users.