Expert Oracle Exadata - Parent Directory

CHAPTER 7 RESOURCE MANAGEMENTwhen workloads are mixed and you have no applications that require extremelylow latency.Auto: This setting allows IORM to determine the best optimization objective foryour workload. Cellsrv continuously monitors the large/small I/O requests andapplies the optimization method on a best-fit basis. If 75% or more of the I/Ooperations from a consumer group are small I/O (less than 128K), then it isconsidered to be a latency-oriented consumer group and is managed accordingly.The default setting for an IORM plan objective is ‘’ (an empty string). The objective may be set using theCellCLI alter iormplan objective objective command as follows:CellCLI> alter iormplan objective = low_latencyIORMPLAN successfully alteredCellCLI> list iormplan attributes objectivelow_latencyMethods for Managing I/O on ExadataAs introduced earlier, there are three methods for managing I/O on the Exadata platform: InterdatabaseIORM, Category IORM, and Intradatabase IORM. All three address specific needs for managing I/O.Interdatabase IORM allocates I/O resources by database name, Category IORM allocates I/O resourcesby common categories among databases, and Intradatabase IORM manages I/O within the databaseusing DBRM resource groups. You can choose to use any one of the methods for managing your I/Oresources, or you combine them to implement a more sophisticated resource plan. When these methodsare used together, Oracle schedules I/O in the following order: 1) allocation among categories, 2)allocation among databases, and 3) allocation among consumer groups within each category withineach database. We’ll show how all this works a little later.Interdatabase I/O Resource ManagementInterdatabase I/O resource management refers to the IORM feature that manages I/O priority amongmultiple databases by database name. Interdatabase IORM allocates I/O resources across multipledatabases by means of an IORM plan configured on each storage cell. The IORM plan defines allocationpriorities using I/O directives. Each storage cell manages its own I/O queues based on the local IORMplan defined in the cell. IORM plans should be identical for all storage cells in the storage grid. If youhave split your Exadata storage cells into multiple storage grids, then IORM plans may differ from grid togrid, but they should still be identical among storage cell members within each storage grid. We discussconfiguring multiple storage grids in Chapter 14. Figure 7-9 illustrates how I/O allocation policies areorganized within the IORM plan.209