qrdel: 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/qrdel - from package: gridengine
/usr/share/gridengine/bin/lx26-amd64/qrdel - from package: gridengine
/usr/share/gridengine/bin/lx26-x86/qrdel - from package: gridengine

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

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