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

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

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