About memory configuration parameter on each PDBs (Doc ID 2655314.1)

Last updated on NOVEMBER 20, 2023

Applies to:

Symptoms

In Database Reference 12.2 and later mentioned that the sum of below parameters on PDBs are managed considering the configuration of CDB.

- SGA_TARGET
- SGA_MIN_SIZE
- SHARED_POOL_SIZE
- DB_CACHE_SIZE

Ex)

Oracle Database Database Reference 12c Release 2 (12.2) E85634-06

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/refrn/SHARED_POOL_SIZE.html#GUID-6D9E390B-472A-46C4-B89B-E263492FCB4F

1.297 SHARED_POOL_SIZE
---
If SGA_TARGET is set at the CDB level, these requirements must be met:
The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than
or equal to 50% of the PDB¿s SGA_TARGET value.
The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than
or equal to 50% of the SGA_TARGET value at the CDB level.
The sum of DB_CACHE_SIZE plus SHARED_POOL_SIZE across all the PDBs in a CDB
must be less than or equal to 50% of the SGA_TARGET value at the CDB level.
If any of these three requirements above are not met, you will receive an
error.
---

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/refrn/DB_CACHE_SIZE.html#GUID-68F83472-D74F-4C1D-B515-FC80C40CC61B

1.68 DB_CACHE_SIZE
---
If SGA_TARGET is set at the CDB level, these requirements must be met:
The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than
or equal to 50% of the PDB¿s SGA_TARGET value.
The values of DB_CACHE_SIZE plus SHARED_POOL_SIZE in a PDB must be less than
or equal to 50% of the SGA_TARGET value at the CDB level.
The sum of DB_CACHE_SIZE plus SHARED_POOL_SIZE across all the PDBs in a CDB
must be less than or equal to 50% of the SGA_TARGET value at the CDB level.
If any of these three requirements above are not met, you will receive an
error.

However, if configuring like as belows, any ORA errors are not caused and database can be started up successfully.

  Example)

   1) The sum of SHARED_POOL_SIZE and DB_CACHE_SIZE of each PDBs is over the value of 50% of SGA_TARGET on CDB.

   2) The sum of DB_CACHE_SIZE of each PDBs is over the value of 50% of SGA_TARGET on CDB.

Cause

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