The DDL models are under
PeopleTools > Utilities > Administration > DDL Model Defaults
Select the Oracle platform from the search, and you should get a scroll with 5 rows. Rows 4 and 5 should begin with DBMS_STATS.GATHER_TABLE_STATS
You can also consider downloading the following tool from Oracle Support:
pscbo_stats - Improving Statistics in Oracle RDBMS for PeopleSoft Enterprise [ID 1322888.1]
See PeopleSoft Database Update Statistics for more information.