The three basic tools on the Solaris platform that are invaluable at this time are:
1. vmstat - gives CPU stats, memory utilization
2. iostat - Gives I/O stats
3. netstat - gives network stats.
This link gives good info on understanding the thump rules to apply to analyze the output of these commands.
Another command that is very powerful on solaris is the 'prstat' command. prstat is more versatile than 'top' that is present on most unix systems.
To find out the top 5 processes consuming CPU time:
prstat -s cpu -a -n 5
To find out the top 5 processes consuming most memory:
prstat -s size -n 5
To dump the CPU usage of a process every 15 secs to a file
prstat -p 2443 15 > server.out &
A very nice feature of prstat is that by using the -L switch, prstat will report statistics for each thread of a process.
prstat -L -p 3295
The following links also provide good info about some basic troubleshooting tips: