Hello,
You are not required to put an end of tape marker. Please verify the append settings. This will rendre the tape appendable. However if this is the first time Backup Exec is ercognising the tape the first operation will be an overwrite operation. Please refer the following documents for further clarification.
Title:
An explanation of the "Overwrite Protection Period" and the "Append Period"
http://support.veritas.com/docs/237374
Title:
The basics of Advanced Device and Media Management for Backup Exec for Windows Servers
http://support.veritas.com/docs/192265
NOTE : If we do not receive your reply within two business days, this post would be marked assumed answered and would be moved to answered questions pool.
