The manual (Performance Guide) say a lot things about guide lines to update statistics and have some articles on IBM site about this.
But, the basic guide lines are:
Medium and big tables:
- update statistics HIGH in head columns (first columns) from any index
- update statistics medium to another's columns where is part of a index
- update statistics medium to columns where is used to filter.
to small tables:
- update statistics high , all columns
Execute update statistics more frequently on tables where the data are modified frequently.
if you have a table with all move of a stock system , and all days have delete/inserts/updates on this table, consider executing the update statistics at least 1 time for week.
This is very hard to say, this can variable in each environment.
but, my personal opinion, this is almost ok, missing only the update statistics low for all tables first , and the update statistics HIGH to all head index columns
Tip, when you put the update statistics , if no user are using the database, use the SET PDQPRIORITY 100 , and review your configurations of PDQ on your ONCONFIG. This will boost the time execution from your update statistics