Rather than letting Oracle determine if full database caching is appropriate, you can force the decision using the command. If the database is open in this or any other instance you get an error message. To force full database caching, you will need to do the following. After that, the change will be visible in the view.

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SQL> ALTER DATABASE FORCE FULL DATABASE CACHING;
ALTER DATABASE FORCE FULL DATABASE CACHING
*
ERROR at line 1:
ORA-01126: database must be mounted in this instance and not open in any
instance

SQL>

CONN / AS SYSDBA
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE FORCE FULL DATABASE CACHING;
ALTER DATABASE OPEN;

SELECT force_full_db_caching FROM v$database;

FOR
---
YES

SQL>

Disabling force full database caching mode follows a similar format. The change is reflected in the view.

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CONN / AS SYSDBA
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE NO FORCE FULL DATABASE CACHING;
ALTER DATABASE OPEN;

SELECT force_full_db_caching FROM v$database;

FOR
---
NO

SQL>

- The parameter must be set to 12.0.0 or higher. - If you are using AMM (MEMORY_TARGET) or ASMM (SGA_TARGET) it is possible the buffer cache size will alter, making the cache too small to hold the entire database. Either size the memory parameters appropriately, or better still set the minimum size of the buffer cache by setting the parameter to an appropriately large value. - There is no pre-emptive loading of objects. Instead, objects are cached as they are accessed. - LOBs defined as NOCACHE can be cached when force full database cache mode is enabled. Under normal running they are not. - Enabling force full database cache mode applies to the CDB and all PDBs when using the multitenant option. - If you need to recover your controlfile, you should check that force full database cache mode is still enabled. For more information see: - Using Force Full Database Caching Mode Hope this helps. Regards Tim...