How does one monitor and trace Unix processes?

To trace what a Unix process is doing enter:

truss -rall -wall -p <PID>
truss -p $ lsnrctl dbsnmp_start

NOTE: The "truss" command works on SUN and Sequent. Use "tusc" on HP-UX, "strace" on Linux, "trace" on SCO Unix or call your system administrator to find the equivalent command on your system.

Monitor your Unix system:

Unix message files record all system problems like disk errors, swap errors, NFS problems, etc. Monitor the following files on your system to detect system problems:

tail -f /var/adm/SYSLOG
tail -f /var/adm/messages
tail -f /var/log/syslog