hello,
# dfm perf data list ( this shows collection perdiod ( secs))
to change Performance Data Retention Times for "iSCSI Basic" ( for exemple) :
# dfm perf data modify "iSCSI Basic" collectionPeriod=7776000
--> ======== In oncommand Core Package
# dfm perf data modify -G iscsi -o <hostname> -r 90d