Re: nonlogged blocks despite force logging

  • From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Fri, 26 Nov 2021 15:56:42 -0500

On 11/26/21 10:37, Noveljic Nenad wrote:

What might be the explanation for non-logged blocks if logging is forced on the database level?


SQL> select count(*) from v$nonlogged_block ;






SQL> select force_logging from v$database ;






The non-logged blocks belong to a LOB segment:


1* select segment_name,segment_type from dba_extents where file_id = 11 and 137828 between block_id and block_id + blocks  -1

SQL> /



------------------------------ ------------------

SYS_LOB0000006331C00004$$      LOBSEGMENT


It started happening after migrating from 19.7 non-cdb to 19.13 multi-tenant.


Best regards,




Based on your description and the very low number of unlogged blocks, I would say, you've encountered the following bug:

Bug 9766652 - If a lob column is modified to 'cache reads' or 'nocache', the logging attribute for the lob index may be unexpectedly changed to 'nologging' (Doc ID 9766652.8) To Bottom

Of course, I cannot be sure, you will probably have to open a SR with Oracle Support. Regards

Mladen Gogala
Database Consultant
Tel: (347) 321-1217
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