A write window is the amount of time the tape can be appended to, assuming it isn't full. So let's assume you have a write window of 7 days. The backups will write to that tape for 7 days, or until the tape is full. After 7 days the write window will close, so no more backups will write to that tape until it expires.
It is at that time that the retention (keep) period starts. So if the keep retention is set to 10 days, the tape will not expire for a futher 10 days. So in total your tape will be active for 17 days.
Hope that helps.
Thank you for response.
Q1. And then, If I make a write windows to 7 days but tape is full while 2days, what happened?
The retestion(keep) period started inspite of 5days remains? or started after 5 days later?
Q2. I'm confused regarding write windows. If I want keep backup image 14 days, How to decide write windows period?
I didn't know size of backup exactly and Just want to keep image during 14 days after last backup image on media.(to recycle media after 14days)
If I have a daily full backup schedule and want to use full area of tape media, I don't know how many daily backup(image) can write to that media,
Just want to use tape to end of tape(Full) and start to retention(keep) period from that time.
Please advice how to make this?
Is it good choice to make a policy as 13days write windows and 1 days keep time?
I sorry to bothering you.
Thank you very much.
The retention period starts as soon as the write window closes, it doesn't matter if the tape becomes full, the write window remains the same so the tape will close on that date. You can do an "obtool lsvol -l" on a tape and see when it will close and when it will expire :
obtool lsvol -l -b ADC00003
Volume OID: 29091
Volume ID: FullBackups-002467
Volume sequence: 2
Media family: FullBackups
Closes: 2014/03/18.04:01 (closed)
Space remaining: none
Original OID: 29091
If you want a backup to be kept for exactly 14 days then your write window+retention needs to equal 14, so it could be 7+7. 13+1 is also fine, assuming you are not looking to send the tapes out of the library, and that will also ensure your tapes are used to their capacity.