pcp_pool_status: 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_pool_status - 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_pool_status - from package: pgpool2

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

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