How v$recovery_file_dest.space_used is calculated from v$asm_file.bytes in ASM
(Doc ID 1212079.1)
Last updated on JANUARY 24, 2020
Applies to:Oracle Database - Enterprise Edition - Version 184.108.40.206 and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Information in this document applies to any platform.
The purpose of this note is to provide insight on how space allocation ( v$asm_file.space column ) in ASM can be calculated depending on Allocation Unit size, redundancy and striping scheme.
There will be big space gap for Flashback logs in recovery destination diskgroup as the default redundancy and striping method for Flashback logs are "Fine" and "High" and the way of how v$recovery_file_dest.space_used is calculated in ASM. As a result of this space gap, recovery destination clean up mechanism sometimes won't kick in even db_recovery_file_dest_size is used up.
db_recovery_file_dest_size should be calculated carefully by taking into account redundancy, striping and AU boundary as it can cause database hung in a situation when archivelog can not be generated.
This note will be useful -
1. Calculate the exact size of a file in ASM environment.
2. Calculate v$recovery_file_dest.space_used for flashback logs and archived log files.
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