Deleting Expired Backupsets From Single .BAK File

Hi,

I'm new to SQL Server 2005 (up until now I've been an Oracle DBA exclusively) and have been tasked with backing up all (6) of our SQL Server 2005 databases on a regular basis. To accomplish this, I've created individual SQL Server jobs for each database I wish to backup. Each of these jobs executes a T-SQL script like this:


BACKUP DATABASE [MYDATA] TO DISK = N'\networksharemydata.bak' WITH RETAINDAYS = 4,
NOFORMAT,
NOINIT,
NAME = N'MyData-FullBackup',
SKIP,
NOREWIND,
NOUNLOAD,
STATS = 10
GO


My goal in specifying 'RETAINDAYS = 4' was so that there would always be 4 days worth of "backupsets" (forgive my Oracle-ese) kept in mydata.bak. But when I look at the amount of backupsets kept in mydata.bak I noticed that all of them were being kept and none were being deleted.


I researched this problem a little bit and thought I had discovered a solution by specifying 'INIT' instead of 'NOINIT' and 'NOSKIP' instead of 'SKIP', but this deletes the entire contents of mydata.bak only-if all of the backupsets contained in it are past their expiration date. I was hoping it would just delete the expired backupsets and keep the non-expired ones, but this isn't the case.


Does anyone know the simplest way - with T-SQL commands - to accmplish the task of backing up a database to 1 individual .bak file and also only retain x amount of "backupsets" within it? Any help would be greatly appreciated, and the more detailed the better. Thanks.


- Gary