Using HP PRM with Oracle Databases

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Total resource isolation
Total resource isolation means that a single Oracle database instance runs in a PRM group that has
access to a fixed pool of cores and private memory. The PRM group cannot loan these resources to
other PRM groups, nor can it borrow additional resources from other PRM groups. If cores are not
used, they go idle. If memory is not used, it is wasted. However, both cores and memory remain
dedicated to the Oracle instance running in the associated PRM group.
To achieve total resource isolation, you:
• Assign the Oracle database instance to a pSet PRM group, providing isolation of the CPU resource
• Enable the MRG private memory isolation feature, providing isolation of the memory resource
PRM’s application manager, when combined with the MRG private memory isolation and pSet
features of PRM, can be used to completely isolate and manage resource allocation for multiple
instances of Oracle databases. The Oracle Database Resource Manager can then be used to
independently allocate resources to applications and users of an Oracle instance within the context of
a pSet.
NOTE
You do not have to use private memory isolation when using CPU resource
isolation. With private memory isolation, your database instance is not
affected by the memory use of any other workload on the system. However,
it also cannot borrow unused resources from other workloads. Without
private memory isolation, your instance can take advantage of unused
memory when doing a large sort or select. However, performance will be
inconsistent because the extra memory might not always be available.
You can dedicate a minimum amount of shared memory to a pSet PRM group—on a group-by-group
basis. This feature enables you to manage an instance’s SGA.
Advantages
The advantages of total resource isolation are:
• Fixed and unchanging CPU and memory resource entitlements allow for more deterministic
behavior because surplus CPU and memory resources are not available and any loaned-out
resources do not have to be reclaimed when needed.
• Support for the Oracle Database Resource Manager because PRM and the Database Resource
Manager are in agreement on what CPU and memory resources are available.
• Support for Oracle 9i (and later) Program Global Area (PGA) memory management. When long
queries are run, Oracle processes can relinquish memory during or after a query so that other
processes within the same instance can use this memory. Without memory isolation, there is no way
to guarantee that other processes in the same instance will use this newly freed memory.
Disadvantages
The disadvantages of total resource isolation are:
• Resources are wasted because unused memory and CPU cycles go idle or are not used.
• The CPU resource can only be allocated in course-grained chunks based on the core. A fraction or
percentage of a core cannot be allocated to a pSet PRM group.