Here is a link to give you information on prestart jobs: http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=/rzaii/rzaiimstprestrtjob.htm
An Autostart job is a job you create and add to a subsystem description. Then when a STRSBS is run, you job will kick off automatically.
They are just jobs that you want to always be running when the system is started. They are “back-end” batch “servicing” jobs such as queue monitors.
Pre-Start Job: A prestart job is a batch job and will run on the server before a program on a remote system tries to connect with that server. Usually multiple prestart jobs of a particular type are configured to run. Prestart jobs are run to increase performance of initiations and connections to a server.
Autostart Job: An autostart job starts automatically when the subsystem it is associated with starts. These jobs generally perform initialization work that is associated with a particular subsystem. Autostart jobs can also perform repetitive work or provide centralized service functions for other jobs in the same subsystem. The subsystem job uses information from the autostart job entry in the subsystem description, when starting a job.
Note: All autostart jobs are started when the subsystem starts.