whichdb: 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 Debian possible default full paths are:

/usr/bin/whichdb - from package: emboss

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

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