Oracle Database is moving to Cloud and with that Oracle DBA Role is moving to Oracle Cloud DBA. With DBA & Cloud DBA being in-demand skill but very competitive too. In order for you to stand out from crowd, stay ahead be hired first its important that you get yourself Oracle Database Cloud Service Certified [1Z0-160]
Note: For normal Oracle DBA, there are three Certification levels OCA, OCP & OCM. When you clear Oracle Exam 1Z0-160 and
- If you are not already OCA/OCP/OCM in DBA, then you get Oracle Database Cloud Service Operations Certified Associate
- If you are already OCA certified in DBA, then you get Oracle Database Cloud Administrator Certified Associate
- If you are already OCP certified in DBA, then you get Oracle Database Cloud Administrator Certified Professional
We recently launched our Oracle Database Cloud Service Certification [1Z0-160] Training Program only to selective existing list and within 3 days fully booked and almost all those who went through certification cleared but their main concern (including my own) was about about Performance Tuning related questions (Managing Multiple PDCs on CDB in Database Cloud Service on Oracle Public Cloud)
Purpose of this post is to cover Performance Tuning related topic (Resource Manager) from Oracle Database Cloud Certification [1Z0-160] , You will get few questions from this topic in Certification Exam so make sure you understand it thoroughly (We now added two dedicated module on this topic now in our Certification [1Z0-160] Training Program).
Multi-Tenant Architecture (CDB & PDB)
Oracle Database 12c comes with Multi-Tenant Architecture containing Container Database(CDB) containing container(tenant) residing inside it called as Pluggable Database(PDB). These PDB databases contain the schemas and data for your applications. More on Multi-Tenant Architecture in Oracle 12c here.
Performance Issues: Multiple PDBs in CDB
In a CDB with multiple PDBs, multiple workloads (running SQL command or background Jobs or gather schema) for multiple PDBs can compete for System and CDB resources. When resource allocation decisions for a CDB is dealt by the operating system, the following workload-management-related issues can arise:
Workload Management related Issues:
- Inappropriate allocation of resources among PDBs. One or more PDBs might use a significant amount of system resources, leaving the other PDBs starved for resources.
- Inappropriate allocation of resources within a single PDB. One or more sessions connected to a single PDB might use a significant amount of system resources, leaving the other sessions that are connected to the same PDB starved for resources.
- Inconsistent performance. A single PDB might perform inconsistently when other PDBs are competing for system resources at various times.
- Lack of resource usage data for PDBs. Operating system monitoring tools can gather resource usage data for a single non-CDB running on a system. However, operating system monitoring tools are not as effective in monitoring a CDB, because there are multiple PDBs running in the CDB on the system.
How Resource Manager Helps:
- Resource Manager helps address these issues by giving the CDB more control over how hardware resources are allocated among and within PDBs.
- In a CDB with multiple PDBs, some PDBs are typically more important than others are. Resource Manager enables you to prioritize and limit the resource usage of specific PDBs.
- In Oracle Database 12c, Resource Manager can be used to prioritize and limit resource usage for competing workloads within a PDB and for competing PDBs in a CDB.
- Resource Manager works at two levels: the CDB level and the PDB level.
- At the CDB level, it prioritizes resources by limiting resource utilization for a PDB or PDBs in a CDB.
- At the PDB level, it manages the workloads within each PDB by limiting the resource utilization for a workload.
With a CDB-level resource plan, You can:
- Specify shares of system resources so that more resources are allocated to more-important PDBs (By default, all PDBs have equal shares.)
- Limit the CPU usage of a particular PDB
- Limit the number of parallel execution servers a particular PDB can use
- Limit the resource usage of different sessions connected to a single PDB
- Monitor the resource usage of PDBs
With a PDB-level resource plan, You can:
- A CDB-level resource plan specifies the number of resources allocated to each PDB. A PDB-level resource plan can be used to allocate resources among the consumer groups (a maximum of eight) within a PDB. The plan cannot have sub plans or a multiple-level scheduling policy.
- A PDB-level resource plan is similar to a resource plan for a non-CDB. A PDB-level plan allocates resources among the consumer groups within a PDB from the shares of resources allocated to a PDB by a CDB-level plan. When you create one or more PDB-level resource plans and there is no CDB resource plan, the CDB uses the DEFAULT_CDB_PLAN supplied with Oracle Database.
As you have got bit idea of CDB and PDB level resource plan, lets discuss two sample Quiz from our DBCS Certification [1Z0-160] Training Program .
Q1: Which two statements are true about a PDB-level resource plan?
- It can be used to allocate resources across all PDBs in a CDB.
- It can be used to limit the resource utilization for a workload in a PDB.
- If a PDB-level plan is enabled, Resource Manager will use resource allocation at the PDB-level plan and ignore the limits set at the CDB level.
- If a PDB-level plan is not enabled, Resource Manager will allocate equal resources to all sessions for that PDB.
- If no PDB plan is enabled for a PDB, Resource Manager will allocate resources based on the CDB-level plan.
A1. The correct answers are 2 and 4.
- Option 1 is incorrect because the PDB-level plan prioritizes only the workload within a particular PDB and not for other PDBs in a CDB.
- Option 2 is correct because the PDB-level plan can be used only to limit resource utilization for consumer groups within that PDB.
- Option 3 is incorrect because if the PDB-level plan is enabled, it will be able to use only the resources allocated to a PDB by the CDB-level plan.
- Option 4 is correct because if no PDB-level plan is enabled, all sessions will be allocated resources equally.
- Option 5 is incorrect because if no PDB-level plan is enabled, all the sessions for a PDB will be allocated equal shares of the resources allocated to that PDB by a CDB-level plan.
Now that you have learned about resource management plans, you should be able to answer the below question that you may expect in Oracle Database Cloud Service Certified [1Z0-160].
Q2: You get complaints from users of several different applications that performance has degraded over time. These applications run in this configuration: A check of wait events for the sessions belonging to these applications shows that the sessions are waiting longer and that there are more sessions from other applications in the same database instance. You wish to avoid scaling up your Database as a Service (DBaaS) instance in Oracle Cloud. Which four should you check and possibly reconfigure to avoid the need to scale up the DBaaS instance?
- Modify the users that are using each application so that their sessions are associated with the correct consumer group in the PDB that is hossting their application.
- Check the CDB plan to configure the shares allocated to all PDBs, including the PDBs that contain the two poorly performing applications.
- Check the CDB plan only to configure the shares allocated to the PDBs that contain the two poorly performing applications.
- Create separate consumer groups for the sessions for all applications in the PDB plans for the PDBs that are hosting the two poorly performing applications.
- Check the PDB plan for all the PDBs in the CDB, including the PDB that is hosting the two poorly performing applications.
- Create a PDB plan for each PDB in the CDB that has poorly performing applications.
- Create a separate CDB plan for each PDB that has poorly performing applications
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