1) What is an Pluggable database really?
Ans-> This is new feature in oracle 12.1 release with respect to database. With this release there is a parent-child relationship between databases. I.e. One database act as Container(Parent) and rest act as its child(Pluggable) databases. We can have n number of pluggable databases for one container database. Container database are the root can contains the Data dictionary as a whole. However pluggable database refer to containers database data dictionary.
Pluggable databases shares some common users with container(ROOT) database like SYS,SYSTEm users.
2) Does my pluggable database contain user datafiles as any other pre-12c database?
Ans-> Pluggable database has its own set of user datafiles and tablespaces
3) Does pluggable database contain Temporary files?
Ans-> Container database holds the temporary file as a whole and all other pluggable database shares those tempfile. But we can create tempfiles for each individual pluggable database
4) Does pluggable database contain UNDO tablespace?
Ans=> No it doesn’t however UNDO tablespace of Container share it with other pluggable database
5) Can we have pluggable database without Container database?
Ans-> No we cannot have pluggable database without Container database.
6) Can container database have no pluggable database?
Ans-> No Container also doesn’t comes without pluggable database. When we install Container database, one implicit SeeD Pluggable database created by default.
7) What is Seed database?
Ans-> Seed database is a pluggable database which comes by default with Container database. Seed database act like a template and can be used to create other non-default pluggable databases
8) Can we remove SeeD database?
Ans-> No we cannot remove it
9) Are there any background processes for Pluggable database like DBWR?
Ans-> No there are no background processes available for pluggable database like we have for any other database. Background process runs for main container database and shares these with pluggable database. So background process like DBWR belongs to container database and do its task to write dirty blocks from SGA to disk. It also writes to user datafiles which belongs to pluggable database
10) Does pluggable database have its SGA and PGA?
Ans-> No Pluggable database doesn’t have its own set of SGA and PGA. However all pluggable database shares the SGA of Container Database. So SGA of container database is shared among other pluggable database
11) Can we create user defined datafiles inside container database?
Ans-> Yes we can create user defined datafiles and tablespaces for container database but its highly recommended not to create any user tablespaces inside CDB bacuse pluggable database purpose is to hold user data
12) Can we use SeeD database for users data?
Ans-> Yes we can use it for user data
13) Do we need separate REDO logs for each pluggable database?
Ans-> No, we cannot create separate REDO logfiles for each pluggable database because REDO belongs to CDB and there is only one set of REDO logs belongs to CDB
14) Does Pluggable database contain controlfiles?
Ans-> No. Controlfiles belongs to CDB only
15) What tablespaces are created by default with Pluggable database?
Ans-> SYSTEM, SYSAUX
16) Do we need separate Listener for each pluggable database
Ans-> There is only one listener.ora file for CDB as a whole. So all other pluggable database uses common listener. Therefore listener.ora and tnsnames.ora reside under CDB
17) Does PDB has alertlog and traces by itself?
Ans-> There is only one alert.log for all PDB which is maintained under CDB. Pluggable database sends message and alerts to CDB’s alert.log
Reference - MOS - FAQ Pluggable database
2) Does my pluggable database contain user datafiles as any other pre-12c database?
Ans-> Pluggable database has its own set of user datafiles and tablespaces
3) Does pluggable database contain Temporary files?
Ans-> Container database holds the temporary file as a whole and all other pluggable database shares those tempfile. But we can create tempfiles for each individual pluggable database
4) Does pluggable database contain UNDO tablespace?
Ans=> No it doesn’t however UNDO tablespace of Container share it with other pluggable database
5) Can we have pluggable database without Container database?
Ans-> No we cannot have pluggable database without Container database.
6) Can container database have no pluggable database?
Ans-> No Container also doesn’t comes without pluggable database. When we install Container database, one implicit SeeD Pluggable database created by default.
7) What is Seed database?
Ans-> Seed database is a pluggable database which comes by default with Container database. Seed database act like a template and can be used to create other non-default pluggable databases
8) Can we remove SeeD database?
Ans-> No we cannot remove it
9) Are there any background processes for Pluggable database like DBWR?
Ans-> No there are no background processes available for pluggable database like we have for any other database. Background process runs for main container database and shares these with pluggable database. So background process like DBWR belongs to container database and do its task to write dirty blocks from SGA to disk. It also writes to user datafiles which belongs to pluggable database
10) Does pluggable database have its SGA and PGA?
Ans-> No Pluggable database doesn’t have its own set of SGA and PGA. However all pluggable database shares the SGA of Container Database. So SGA of container database is shared among other pluggable database
11) Can we create user defined datafiles inside container database?
Ans-> Yes we can create user defined datafiles and tablespaces for container database but its highly recommended not to create any user tablespaces inside CDB bacuse pluggable database purpose is to hold user data
12) Can we use SeeD database for users data?
Ans-> Yes we can use it for user data
13) Do we need separate REDO logs for each pluggable database?
Ans-> No, we cannot create separate REDO logfiles for each pluggable database because REDO belongs to CDB and there is only one set of REDO logs belongs to CDB
14) Does Pluggable database contain controlfiles?
Ans-> No. Controlfiles belongs to CDB only
15) What tablespaces are created by default with Pluggable database?
Ans-> SYSTEM, SYSAUX
16) Do we need separate Listener for each pluggable database
Ans-> There is only one listener.ora file for CDB as a whole. So all other pluggable database uses common listener. Therefore listener.ora and tnsnames.ora reside under CDB
17) Does PDB has alertlog and traces by itself?
Ans-> There is only one alert.log for all PDB which is maintained under CDB. Pluggable database sends message and alerts to CDB’s alert.log
Reference - MOS - FAQ Pluggable database
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