Expert Oracle Exadata - Parent Directory

CHAPTER 7 RESOURCE MANAGEMENTrelationship between a plan directive and a consumer group, and no two directives may be assigned tothe same resource group (within the same plan). A plan directive is made up of a list of managementattributes in a key=value fashion. For example, the following listing shows how a set of directives may bedefined in DBRM:DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE(PLAN=> 'example_plan',GROUP_OR_SUBPLAN => 'APPS',COMMENT=> 'OLTP Application Sessions',MGMT_P1 => 70,MAX_UTILIZATION_LIMIT => 90,MAX_EST_EXEC_TIME => 3600);MGMT_PnExadata’s IO Resource Manager works with DBRM through plan directives using the CPU managementattributes MGMT_Pn, (where n may be 1–8), and MAX_UTILIZATION_LIMIT, so going forward these attributeswill be the focus our discussion. CPU is allocated in a level + percentage manner. Usage of the MGMT_Pnattribute determines the relative priority in which CPU is allocated to consumer groups across thevarious levels, where 1 is the highest level/priority. The percentage assigned to the MGMT_Pn attributedetermines how available CPU resources (unallocated plus unused) are allocated within a particularlevel. Whatever CPU is unused or unallocated from level 1 is allocated to level 2. Unused and unallocatedCPU from level 2 is then passed to the consumer groups on level 3. If there are two consumer groups onlevel 2 and one of them doesn’t use its allocation, the unused CPU is always passed to the next level inthe Plan. The other consumer group on level 2 can’t utilize it.Figure 7-1 shows a simple resource plan and illustrates how this level + percentage method ofallocating CPU resources works.MGMT_P1Management AttributesMGMT_P2MGMT_P3ConsumerGroupLevel 1 CPUAllocationLevel 2 CPUAllocationLevel 3 CPUAllocationResource DirectivesAPPS 70%REPORTSMAINTENANCEOTHER_GROUPS50%50%50%Figure 7-1. Resource directivesIn Figure 7-1 the APPS group is allocated 70% of total CPU available to the database. Sessions in theREPORTS group are the next highest priority at level 2 and will be allocated half of the unallocated CPU(30%) from level 1. Sessions in the resource groups MAINTENANCE and OTHER_GROUPS equally shareunallocated CPU (50%) from level 2. This can be expressed in formula form as follows:APPS = 70% (100% × 70%)REPORTS = 15% ((100% – 70%) × 50%)182