pcp_proc_count: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pcp_proc_count - from package: postgresql-pgpool-II

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/pcp_proc_count - from package: pgpool2

You may install the required package with command apt-get install {package}

Error in other languages:
pcp_proc_count: bevel nie gevind nie
pcp_proc_count: comandă negăsită
pcp_proc_count: comando não encontrado
pcp_proc_count: commande introuvable
pcp_proc_count: command not found
pcp_proc_count: käsku ei ole
pcp_proc_count: không tìm thấy lệnh
pcp_proc_count: komanda nerasta
pcp_proc_count: Kommando nicht gefunden.
pcp_proc_count: kommandot finns inte
pcp_proc_count: komut yok
pcp_proc_count: nie znaleziono polecenia
pcp_proc_count: níor aimsíodh an t-ordú
pcp_proc_count: no se encontró la orden
pcp_proc_count: no s'ha trobat l'ordre
pcp_proc_count: opdracht niet gevonden
pcp_proc_count: parancs nem található
pcp_proc_count: perintah tidak ditemukan
pcp_proc_count: príkaz nenájdený
pcp_proc_count: příkaz nenalezen
pcp_proc_count: команда не найдена
pcp_proc_count: командата не е открита
pcp_proc_count: 命令找不到
pcp_proc_count: コマンドが見つかりません