PDB doesn't take underscore parameters during database start

Question

Hello
All underscore parameters which are set on a PDB level are ignored during database start.
An underscore parameter is set on a PDB level in memory and spfile. After restarting database the parameter is still in pfile but not anymore in memory.
SQL> show pdbs
    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
         2 PDB$SEED                       READ ONLY  NO
         3 Q00A                           READ WRITE NO
SQL> alter session set container=Q00A;
SQL> alter system set -_push_join_union_view-=FALSE scope=both sid='*';
SQL> show parameter -_push_join_union_view-
NAME                                 TYPE        VALUE
_push_join_union_view                boolean     FALSE
SQL> show spparameter -_push_join_union_view-
SID      NAME                          TYPE        VALUE
*        _push_join_union_view         boolean     FALSE
srvctl stop db -d cdbq00r; srvctl start db -d cdbq00r
SQL> show parameter -_push_join_union_view-
no rows
SQL> show spparameter -_push_join_union_view-
SID      NAME                          TYPE        VALUE
*        _push_join_union_view         boolean     FALSE
Thanks
Venkat

Answer 1

In the future please post multitenant questions in the Multitenant forum
Multitenant
Based on what you posted we can NOT tell WHAT database/PDB that last command is showing data for or what DBs are being started and opened.
A STARTUP command only starts/opens the root/CDB by default. It does NOT open ANY PDBs.
If you want PDBs to be opened at startup you need to create an AFTER STARTUP trigger to open them.
The code you posted shows a startup but does NOT show if the PDB is open and does NOT show that the current container is the PDB when you check that parameter.
Rerun your test and post ALL of the info needed that shows:
1. the PDB is actually being opened,
2. the current container is set to the PDB
3. the value of the parameter for that PDB
That is, AFTER you stop/restart the database use EXACTLY the same commands you used at the start: show the pdbs, change the container to the PDB and then show the parameter value.
Post the FULL results of doing ALL of that.