SYS.V_$SYSMETRIC_SUMMARY metrics

I have been reading ‘response-time analysis made easy in oracle 10g’ .
http://www.oracle.com/technology/pub..._analysis.html


Can somebody tell me what the definition of the 'Response Time Per Txn’ metric from SYS.V_$SYSMETRIC_SUMMARY exacltly is ?
i.e Does this include select transactions or is it only insert,update and deletes ?

Also do you know where i can find the definition of all metrics from SYS.V_$SYSMETRIC_SUMMARY as i have searched Oracle doc and cannot find.

thanks

Dermot