Tape backup initialization problem

Hi,

we are wrking on ECC 6.0 and Oracle 10g on windows 2003 server.

We are using 6 tapes to take backup from Monday to saturday and in ora<SID>.SAP

expire_period is set to 6.

Now the backup works fine from Monday to saturday with initilization tape.

But whenever we repeat tht is come back to monday we need to initialize every time we take backup otherwise it givs tape vol name error.

any body any idea plz ????/

Regards

Manish