mono-heapviz: 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/mono-heapviz - from package: mono-core

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

On Debian possible default full paths are:

/usr/bin/mono-heapviz - from package: mono-devel

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

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