On the previous release it was possible to create a resource manager CDB resource plan to control the division of CPU and parallel execution server resources between PDBs. This required a separate plan directive for each PDB, which doesn’t scale well to thousands of PDBs. In Oracle Database 12c Release 2 (12.2) it is now possible to create a resource plan based on performance profiles which defines the resource management for groups of PDBs. This can drastically reduce the amount plan directives required to handle thousands of PDBs.
Create CDB Resource Plan with PDB Performance Profiles
The process for creating a CDB resource plan using PDB performance profiles is very similar to using CDB plan directives. Instead of targeting individual PDBs, the profiles define types of PDBs that have the same resource usage profiles. The profile directives allocate shares, which define the proportion of the CDB resources available to the PDB, and specific utilization percentages, that give a finer level of control. PDB performance profiles are managed using the DBMS_RESOURCE_MANAGER package. Each profile directive is made up of the following elements:
- profile : The profile the directive relates to.
- shares : The proportion of the CDB resources available to the PDB.
- utilization_limit : The percentage of the CDBs available CPU that is available to the PDB.
- parallel_server_limit : The percentage of the CDBs available parallel servers (
PARALLEL_SERVERS_TARGETinitialization parameter) that are available to the PDB.
PDBs without a specific plan directive use the default PDB directive.
Posted from: https://oracle-base.com/articles/12c/multitenant-resource-manager-pdb-performance-profiles-12cr2
More on CDB resource plan: shares and utilization_limit:
The CDB resource plan is mainly about CPU. It also governs the degree when in parallel query and the I/O when on Exadata, but the main resource is the CPU: sessions that are not allowed to used more CPU will wait on ‘resmgr: cpu quantum’. In a cloud environment where you provision a PDB, like in the new Exadata Express Cloud Service, you need to ensure that one PDB do not take all CDB resources, but you also have to ensure that resources are fairly shared
Posted from: https://www.dbi-services.com/blog/cdb-resource-plan-shares-and-utilization_limit/