To read settings for one instance:
<db2 install dir>/adm/db2set -i <instance>
and (as instance owner):
db2 get db cfg for <db2 instance>
or (as instance owner, retrieving more details):
db2 connect to <db2 database> db2 get db cfg for <db2 instance> show detail
To read global settings:
<db2 install dir>/adm/db2set -g
db2 connect to <db2 database> db2 "select tbspace, overhead, transferrate from syscat.tablespaces" db2 get snapshot for tablespaces on <db2 database>
db2 list applications show detail
To drop an instance do (as root):
<db2 install dir>/instance/db2idrop <instance>