Cs appointment

Hi,

Please help me regarding the following Query:-

Weather retainership appointment of PCS can be considered as whole time appointment as per CA Act 2013?  

Suppose any Pvt Ltd Co (above 5 Cr Capital) appoint retainership PCS instead of whole time CS.

It is acceptable because as per CA act 1956 lot of cos. following these practices.

Is there any provision for the same?

Please Guide.

Thanks in advance