Setting RMAN recovery window to 2 days make any backup older than 2 days become obsolete is a myth.
See below the scenario which make you understand what need to consider when you are setting RMAN recovery window.
For Non Incremental Level backup
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Assume no backup exist before 13th of Oct
Assume recovery window is 2
POR = Point of recoverability
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date backup type status POR (Current date-recovery window)
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13-OCT-2009 Full backup No obsolete found 13-OCT-2009-2 = 11-OCT-2009
15-OCT-2009 Full backup No obsolete found 15-OCT-2009-2 = 13-OCT-2009
16-OCT-2009 Full backup No obsolete found 16-OCT-2009-2 = 14-OCT-2009
See above table data on 16-OCT-2009 , POR is 14-OCT-2009 and you dont have any backup on 14th of oct within yours backup schedule, in this case 13th Oct backup will enable you POR of 14th Oct , 13th Oct backup will not be marked obsoleted
What would be happen on 17th of october lets see
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date backup type status POR (Current date-recovery window=POR)
-----------------------------------------------------------------------------------------------------------
13-OCT-2009 Full backup No obsolete found 13-OCT-2009-2 = 11-OCT-2009
15-OCT-2009 Full backup No obsolete found 15-OCT-2009-2 = 13-OCT-2009
16-OCT-2009 Full backup No obsolete found 16-OCT-2009-2 = 14-OCT-2009
17-OCT-2009 No backup 13th Oct Full backup 17-OCT-2009-2 = 15-OCT-2009
will be marked
obsoleted
See above table data on 17-OCT-2009 , POR is 15-OCT-2009 you have backup on 15th of oct within yours backup schedule, in this case 13th Oct backup will not be needed for the point of recoverability for 15th of Oct ,15th Oct backup already exist for the POR,15th Oct backup will provide you POR and hence 13th Oct backup will be marked obsoleted.
For Incremental Level backup
================================
Assume no backup exist before 13th of Oct
Assume recovery window is 2
POR = Point of recoverability
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date backup type status POR (Current date-recovery window)
-----------------------------------------------------------------------------------------------------------
13-OCT-2009 L0 No obsolete found 13-OCT-2009-2 = 11-OCT-2009
14-OCT-2009 L1 No obsolete found 14-OCT-2009-2 = 12-OCT-2009
15-OCT-2009 L1 No obsolete found 15-OCT-2009-2 = 13-OCT-2009
16-OCT-2009 L1 No obsolete found 16-OCT-2009-2 = 14-OCT-2009
See above table data on 16-OCT-2009 , POR is 14-OCT-2009 you have backup on 14th of oct within yours backup schedule but this backup is L1 not L0 , in this case 13th Oct backup will be needed for the point of recoverability for 14th of Oct ,13th Oct backup will not be marked obsoleted.
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date backup type status POR (Current date-recovery window)
-----------------------------------------------------------------------------------------------------------
13-OCT-2009 L0 No obsolete found 13-OCT-2009-2 = 11-OCT-2009
14-OCT-2009 L1 No obsolete found 14-OCT-2009-2 = 12-OCT-2009
15-OCT-2009 L1 No obsolete found 15-OCT-2009-2 = 13-OCT-2009
16-OCT-2009 L1 No obsolete found 16-OCT-2009-2 = 14-OCT-2009
17-OCT-2009 L1 No obsolete found 17-OCT-2009-2 = 15-OCT-2009
See above table data on 17-OCT-2009 , POR is 15-OCT-2009 you have backup on 15th of oct within yours backup schedule but this backup is L1 not L0 , in this case 13th Oct backup will be needed for the point of recoverability for 15th of Oct ,13th Oct backup will not be marked obsoleted yet.
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date backup type status POR (Current date-recovery window)
-----------------------------------------------------------------------------------------------------------
13-OCT-2009 L0 No obsolete found 13-OCT-2009-2 = 11-OCT-2009
14-OCT-2009 L1 No obsolete found 14-OCT-2009-2 = 12-OCT-2009
15-OCT-2009 L1 No obsolete found 15-OCT-2009-2 = 13-OCT-2009
16-OCT-2009 L1 No obsolete found 16-OCT-2009-2 = 14-OCT-2009
17-OCT-2009 L1 No obsolete found 17-OCT-2009-2 = 15-OCT-2009
18-OCT-2009 L1 No obsolete found 18-OCT-2009-2 = 16-OCT-2009
19-OCT-2009 L1 No obsolete found 19-OCT-2009-2 = 17-OCT-2009
20-OCT-2009 L0 No obsolete found 20-OCT-2009-2 = 18-OCT-2009
21-OCT-2009 No backup No obsolete found 21-OCT-2009-2 = 19-OCT-2009
22-OCT-2009 No backup obsolete found 22-OCT-2009-2 = 20-OCT-2009
13th L0 and its
alls L1
See above table data on 22-OCT-2009 , POR is 20-OCT-2009 you have L0 backup on 20th of oct within yours backup schedule and this backup is L0 not L1 , in this case 20th Oct backup will be needed for the point of recoverability for 20th of Oct ,before 20th L0 backup 13th L0 backup will marked obsoleted and hence alls its incremental level backup will be marked obsoleted.
