![]() This is a reasonable approach for non-critical systems, because one or more of the instances may frequently be idle or at a very low load. On the other hand, if one of the instances has a period of high load, the CPUs are available to handle it. However, instance caging limits the impact and helps provide somewhat predictable performance. When a server is over-provisioned in this way, the instances can impact each other's performance. For example, on a 4-CPU system with four database instances, you might limit each instance to three CPUs. In this approach, the sum of the CPU limits for each instance exceeds the actual number of CPUs on the system. Over-provisioning-You would use this approach for non-critical databases such as development and test systems, or low-load non-critical production systems. There are two typical approaches to instance caging for a server: Thus, instance caging and the Resource Manager together provide a simple, effective way to manage multiple instances on a single server. This is when the Resource Manager begins to do its work to allocate CPU among the various database sessions according to the resource plan that you set for the instance. When constrained to four CPUs, an instance might become CPU-bound. ![]() In the previous example, if you use instance caging to limit the number of CPUs to four for each of the four instances, there is less likelihood that one instance can interfere with the others. Instance caging is a method that uses an initialization parameter to limit the number of CPUs that an instance can use simultaneously. CPU allocation decisions such as this are made solely by the operating system the user generally has no control over them.Ī simple way to limit CPU consumption for each database instance is to use instance caging. This could degrade performance in the other three instances. For example, on a 16-CPU system with four database instances, the operating system might be running one database instance on the majority of the CPUs during a period of heavy load for that instance. ![]() One resource-intensive database instance could significantly degrade the performance of the other instances. When running multiple instances on a single server, the instances compete for CPU. A typical reason to do so would be server consolidation-using available hardware resources more efficiently. You might decide to run multiple Oracle database instances on a single multi-CPU server.
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