Open extent property handle

The function opens a property handle for the extent or extent based operation path passed in vExtentPath. The operation path may contain symbolic references to option variables (e.g. %EXT_PREF%Pers), which are replaced before evaluating the access path by current settings of corresponding options.

As operation path, a simple property name (extent name), a property path or a path property might be passed as well in vExtentPath.

The extent property is opened with the access mode passed in eAccessMode. The access mode can be changed later on by setting the accessMode() property.

When the extent name (e.g. ImportPersons) refers to an external file (CSV, Directory, XML etc.), an option variable with the extent name has to be defined in the ini-file, database options or application, which refers to the file location (like ImportPersons=~/data/impost/persons.csv).