RMAN-08591: WARNING: invalid archived log deletion policy

Receiving the below error in backup log

Error Details:
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RMAN-08591: WARNING: invalid archived log deletion policy

Cause:
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If archive log location is set to FRA, then there might be a chance of the deleting the archives automatically when the space pressure in FRA.
In that case at least one of the destination standby must be set as a "MANDATORY" destination.

Solution:
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To eliminate the RMAN warning message, at least one archive destination must be set as a mandatory destination.

1. Log in to the broker command line utility

[oracle@prd-srv01 log]$ dgmgrl /
DGMGRL for Linux: Version 12.1.0.2.0 - 64bit Production

Copyright (c) 2000, 2013, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected as SYSDG.
DGMGRL> show configuration

Configuration - prod_dg

  Protection Mode: MaxPerformance
  Members:
  prod - Primary database
    stdby - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS   (status updated 7 seconds ago)

2. For the standby site check the "Binding" property

DGMGRL> show database verbose stdby

Database - stdby

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      11 minutes (computed 0 seconds ago)
  Apply Lag:          0 seconds (computed 0 seconds ago)
  Average Apply Rate: 518.00 KByte/s
  Active Apply Rate:  457.00 KByte/s
  Maximum Apply Rate: 17.62 MByte/s
  Real Time Query:    ON
  Instance(s):
    stdby

  Properties:

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 Binding        = 'optional'
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3. Set the "Binding" property to MANDATORY

DGMGRL> edit database stdby set property Binding='mandatory';
Property "binding" updated

DGMGRL> exit

Once the broker configuration has set a standby site as a mandatory destination, then RMAN will not report this error again.

Reference:
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Data Guard Physical Standby - RMAN configure archivelog deletion policy reports RMAN-08591 (Doc ID 1984064.1)

Happy Learning :)