Exists, System Parameter, Abend, Logged Members

what is the use of exists?
what is the use of system parameter?
if i am running a job with xref, list sysudump, how i can solve the abend? where i have to see the abend details?
i am working in a project. the team members are in different country? how to get the details of the members logged or not?

NOTE : [I][This question was asked by lakshmi_79] [/I]

The main use of system parameter in db2 is that value of system parameters reflects or indicates the operating characteristics of DB2 database. So it is very essential that these system parameters in DB2 must be managed efficiently for proper efficient running of DB2 database.