In CDB database environment, the seed database is always in “READ ONLY” mode. The mode changes only by applying patches using “datapatch”.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 TESTPDB READ WRITE NO
Under the guidance of Oracle Support for specific purpose, the following instructions can be followed to open seed database “PDB$SEED” in “READ WRITE” mode.
Set hidden parameter “_oracle_script” at session level
SQL> alter session set "_oracle_script"=TRUE; Session altered.
Close and then open seed database
SQL> alter pluggable database pdb$seed close immediate instances=all; Pluggable database altered. SQL> alter pluggable database pdb$seed open read write instances=all; Pluggable database altered.
Run the script Oracle support provided
SQL> alter session set container=PDB$SEED; Session altered. SQL> @?/rdbms/admin/catclust.sql ... .. .
Close and then open seed database in READ ONLY mode
SQL> connect / as sysdba SQL> alter session set "_oracle_script"=TRUE; Session altered. SQL> alter pluggable database pdb$seed close immediate instances=all; Pluggable database altered.
SQL> connect / as sysdba SQL> alter session set "_oracle_script"=TRUE; SQL> alter pluggable database pdb$seed open read only instances=all; Pluggable database altered.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 TESTPDB READ WRITE NO
Per Development, setting _ORACLE_SCRIPT to TRUE is something to be used only by Oracle internally. There may be a case where a note says to use it explicitly, but you should not use it outside the context of that note. In general is not to be set explicitly by users.
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