Re: converting string field to type P and increasing length size in dynamic internal table

We can set the field type during the field creation.

DATA: required_type TYPE REF TO cl_abap_elemdescr,

CALL METHOD cl_abap_elemdescr=>get_p

   EXPORTING

     p_length     = Required_length

     p_decimals = Required_decimals

  RECEIVING

      p_result     = required_type.

Also refer the following code snippet which uses different data types for the dynamic field creation

http://wiki.scn.sap.com/wiki/display/Snippets/Example+-+create+a+dynamic+internal+table

Hope it helps