Exam 1z0-083 topic 1 question 161 discussion

DEFAULT_SHARING only aplies to new common objects you create, so it does nothing here. The table was metadata-linked, meaning the app pdbs could have their own data. When we sync the pdb, two things can happen: 1- If table was empty at pdb level, then it wil sync with no errors 2-If table had data at pdb level, it will return: ORA-01758: table must be empty to add mandatory (NOT NULL) column One way to fix this would be to ad a DEFAULT value to the column. There is no 100% correct answer to this question. A: table in app root is empty(because the constraint was added whitout errors), if it had data it would return an error, but it didn't B:It is allowed as long as the data doesnt violate constraints being added... it's not that you cant add constraints to a common object C:No null has been specified for the new column... this doesnt make sense D:No null has been specified for the new column... this doesnt make sense E: Table in root is empty, but still doesnt make any sense... it would return an error if table in root had data. So no correct answers.. :(

DEFAULT_SHARING is only for new objects, so the table is METADATA linked. No data exists in this table for application root, so the ALTER TABLE succeeds. Conclusion is that the rows are inserted via the PDB, hence when SYNCED the error occurs. This is indirectly caused by the table in application root being empty, hence in application pdb not empty. So E.

TL;DR: The A answer should've read: "It will return an error because EMP is not empty in APP_PDB1". The explanation for the error is: when a SYNC starts, it will attempt adding a column to the APP_PDB1.EMP table, however, adding a NOT NULL-constrained column to a non-empty table is errored on every, even a plain, non-APPLICATION PDB-hosted table (try it for yourself). Explanation: there's an error in the offered A answer, to which I arrived by eliminating all the other answers as follows (after fiddling with the assignment):

E. Is the root issue

I think A but not sure why it's not failed at first place. CREATE TABLE test_table ( id NUMBER ); INSERT INTO test_table (id) VALUES (1); commit; ALTER TABLE test_table ADD new_column VARCHAR2(50) NOT NULL; ORA-01758: table must be empty to add mandatory (NOT NULL) column 01758. 00000 - "table must be empty to add mandatory (NOT NULL) column" *Cause: *Action:

I'm not sure of E

General: If a table has already rows inside and you try to add a column with a NOT NULL constraint, then you get an error ORA-01758. So the common table "emp" in app_root must be empty at the moment for the statement: ALTER TABLE emp ADD (sal NUMBER NOT NULL). A - FALSE: The SHARING mode is DATA, so why should an error occurs for the sync statement? B - FALSE: Contraints are allowed: https://docs.oracle.com/en/database/oracle/oracle-database/19/multi/overview-of-the-multitenant-architecture.html#GUID-D9FDDB3D-E3B8-40FA-9EC5-F88467733C92 C/D - FALSE : makes no sense E - FALSE: makes no sense, why should it returns an error due to the table is empty?

A is corect

A in my opinion