remove occurs n

Hello Experts,

I have the current internal table declaration and usage like this:

declaration:

data: m_itab like hie_out occurs 0 with header line.

using in:

1) refresh m_itab

2) select MIED NOISD from Z_RSVD

into table m_ITAB

I am trying to eleminate the 'occurs n' declaration as it is believed to be not good performance.

i replace the declaration statment with

data: m_itab type zmietab.

but i get error at statements 1) and 2)

m_itab is not a internal table specification 'occurs n' is missing.

Any suggestions to get rid of this error..

Thanks,

BWer