4 Replies Latest reply on Aug 18, 2020 11:13 AM by carajandb

    Is it common to have multiple CDBs in a physical server ?

    BlueSkies

      DB version: 19c

      OS version: OL 8.2 (proposed)

      Physical server has 96 CPU cores, 512 GB RAM

       

       

      I am a newbie to the multitenant world.

       

       

      I have a requirement to run 3 OLTP DBs and 1 DWH database in a physical server. All DBs will have the same version (19.3.0.0.0).

      I was hoping to run create one CDB and then create these 4 (3 OLTP + 1 DWH) databases as pluggable databases. But, my Data Warehousing DB has different init.ora requirements like db_block_size=16K. So, I guess, I need to create a separate container database with just one DWH pluggable database. Right ?

       

       

      SQL> select name from v$database;
      
      
      NAME
      ---------
      FRCDB24
      
      
      SQL> 
      SQL> show con_name
      
      
      CON_NAME
      ------------------------------
      FR24TSMPRDPDB
      SQL> 
      SQL> 
      
      
      SQL> select ISPDB_MODIFIABLE, count(*) from v$parameter group by ISPDB_MODIFIABLE order by count(*) desc;
      
      
      ISPDB   COUNT(*)
      -----  ----------
      FALSE      254
      TRUE       191
      
      
      
      
      SQL> show parameter db_block_size
      
      
      NAME                                   TYPE       VALUE
      ------------------------------------ ----------- ------------------------------
      db_block_size                          integer     8192
      SQL> 
      
      

       

       

       

       

      Another related question:

      Is there a list of things which cannot be altered within PDBs, not just initialization parameters? At least the top annoying ones.

        • 1. Re: Is it common to have multiple CDBs in a physical server ?
          Markus Flechtner

          > I have a requirement to run 3 OLTP DBs and 1 DWH database in a physical server. All DBs will have the same version (19.3.0.0.0).

           

          > I was hoping to run create one CDB and then create these 4 (3 OLTP + 1 DWH) databases as pluggable databases. But, my Data Warehousing DB has different init.ora requirements like > db_block_size=16K. So, I guess, I need to create a separate container database with just one DWH pluggable database. Right ?

           

           

          The first aspect of this question is "Licensing":

          Without Multitenant Option, you may have maximum number of 3 PDBs in your CDB.

          So with 4 PDBs you need at least 2 CDBs.

           

          The second aspect are the technical issues.

          Different PDBs may require incompatible settings (software version, database parameters etc.).

          In such a case, you would have to create different CDBs, too.

           

          One of these settings is the default block size of the database:

          All PDBs share the same default block size (which is inherited from CDB$ROOT and which is usually 8192 Bytes).

          Of course, you could add 16K as another block size to your PDBs (by creating a buffer cache for the 16K blocks) and creating tablespaces with the "blocksize" parameter, but I would avoid such a configuration.

           

          So your idea (1 CDB with 8KB-block size for the OLTP PDBs and 1 CDB with 16KB-block size) looks OK.

           

          But instead of using Oracle 19.3.0.0 I would patch the software to the latest RU, 19.7.

           

           

          HTH

          Markus

          1 person found this helpful
          • 2. Re: Is it common to have multiple CDBs in a physical server ?
            BlueSkies

            Thank You Markus.

             

            Yes. My shop is willing to buy multitenant licence. I guess, for 2 CDBs in a server, I would need two multitenant licences. Yet to check with the Oracle Sales guys on all these.

             

            What is "RU" 19.7 ? Is that a new numbering system for quarterly PSU ?

            • 3. Re: Is it common to have multiple CDBs in a physical server ?
              Markus Flechtner

              Hi,

               

              concerning licensing:

              If your system is licensed based on the number of CPUs, you need a multitenant license for your CPUs, but not for an individual database

              (but - as with every licensing question - please ask Oracle for an official statement)

               

              And yes, "RUs" (= Release Updates", are - very roughly - the new name for the quarterly PSUs.

              Please see https://mikedietrichde.com/2017/10/24/differences-psu-bp-ru-rur/  for more information on RUs and the differences between RUs and PSUs.

               

               

              HTH

              Markus

              1 person found this helpful
              • 4. Re: Is it common to have multiple CDBs in a physical server ?
                carajandb

                Hi

                one of my customer has 6 CDBs with about 200 PDBs running on one physical machen (to be more precise: one RAC cluster with Data Guard for Failover). The reasons for this many CDBs are:

                - Database Version (12.1, 12.2, 19c)

                - Patch Level

                - Parameter (one DWH)

                 

                There's no problem at all with this many CDBs as long as you take care of the memory consumption

                 

                Stay healthy

                 

                Johannes