Uses of static mapping = { className cascade: 'delete' }

[R.V.RaguPrashanth]

Greetings Today !!!!!!!!!!!!!!!
class Album
{
String title

static hasMany = [songs:Song]
static belongsTo = [artist:Artist]

static mapping =
{
songs cascade: 'delete'
}
}

what is the usage of cascade: 'delete' function specified in Domain class.