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I'm new to pluggable databases and am puzzled by the dictionary views DBA_PDBS and V$PDBS. What's the differnence? The documentation is not helpful, either:

V$PDBS displays information about PDBs associated with the current instance. 1

SELECT * FROM v$pdbs;

CON_ID  NAME      OPEN_MODE  ...
2       PDB$SEED  READ ONLY  
3       XEPDB1    READ WRITE

DBA_PDBS describes PDBs belonging to a given CDB. 2

SELECT * FROM dba_pdbs;

PDB_ID  PDB_NAME  STATUS ...
2       PDB_SEED  NORMAL
3       XEPDB1    NORMAL

Internally, V$PDBS seems to be based on SYS.X$CON, while DBA_PDBS is based on SYS.CONTAINERS$.

wolφi
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1 Answers1

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There are similar cases with V$DATAFILE vs DBA_DATA_FILES or V$TABLESPACE vs DBA_TABLESPACES: in this case these views data are read from database control files and are likely redundant for restore/recovery purposes (ie when the SYSTEM tablespace is not yet available, DBAxxx views are not there but when database instance needs to work on datafiles and tablespaces). It's likely for the same reason that we have V$PDBS in addition to DBA_PDBS.

pifor
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  • Ah, I see! I never fully understood the difference of v$datafile and dba_data_files, either. Thank you for your explanation! – wolφi May 21 '20 at 13:22