Mainframe, MVS and zOS Discussion

Hi,

How can we get the size of a TAPE dataset on mainframes? Please guide. 

I forgot to mention that I have searched about it, and they talk about looking at Tape Management System. Is that the only solution? And how do I know if I have such a system in our system? Please help.

A tape management system is, by far, the easiest way to get what you want.  Ask someone at your site (system programmer, operator, or other systems person) to find out if your site uses a tape management system.  

If your site doesn't use a tape management system, your next best bet would be to write a program in the language of your choice (SAS or COBOL will both do this) to read the tape dataset and add up the record lengths which will give you approximately the size.  I say approximately because tapes are written in physical blocks and you cannot directly count the blocks.