Command history in Solaris

Can someone tell me what I can do to maintain a single history file ?

As it is it creates a new file for each session.

>ls -a .sh_*
.sh_history.10106 .sh_history.15240 .sh_history.21635 .sh_history.4291
.sh_history.11311 .sh_history.16593 .sh_history.23709 .sh_history.4661
.sh_history.11604 .sh_history.1687 .sh_history.239 .sh_history.6510
.sh_history.11931 .sh_history.17887 .sh_history.26844 .sh_history.8126
.sh_history.1209 .sh_history.18415 .sh_history.27278 .sh_history.8438
.sh_history.12888 .sh_history.19158 .sh_history.28077 .sh_history.9651
.sh_history.13553 .sh_history.19967 .sh_history.28602

I would like it to only keep one file and set the history command count to 100.
Meaning to keep the previous 100 commands. Is that doable is solaris. I know it works in HP.

Thanks in advance.

Please post some more info so folks have a better chance at helping you. Run these commands and post the output:
echo $SHELL
grep -i hist .profile
grep -i hist /etc/profile

>echo $SHELL
/bin/ksh

>grep -i hist .profile
HISTSIZE=128
export HISTSIZE

>grep -i hist /etc/profile
HISTFILE=$HOME/.sh_history.$$
export HISTFILE
### History Commands ###
HISTSIZE=200
export HISTSIZE

It seems it's working they way it is becasue you have it configured that way. One per shell pid.