pva-dbschema-update: command not found

Have You tried accessing the binary with the full path?

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/sbin/pva-dbschema-update - from package: php-voms-admin

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