5.2.3.4 Using the limit Attribute
The limit
attribute specifies the maximum flash I/O
utilization limit as a percentage of the available resources.
You can use the limit
attribute to restrict the
flash I/O utilization for an entity in the interdatabase plan or the cluster
plan. This attribute ensures that the specified entity never utilizes flash
I/O resources beyond the specified limit. The attribute applies only to I/O
on flash devices, which includes flash-based grid disks and Exadata Smart Flash Cache.
For example, if a production and test database are sharing Oracle Exadata Storage Server resources, then you could set a maximum flash utilization limit for the test database in the interdatabase plan as follows:
ALTER IORMPLAN dbplan=((name=prod), -
(name=test, limit=20), -
(name=DEFAULT, limit=10))
If maximum utilization limits are specified, then excess capacity might not be used. As a result, it is possible for flash devices to run below full capacity when maximum utilization limits are specified.
Note:
Specifying lowlimit
values can have a significant performance
impact and is generally not advisable.
Resource management using limits is ideal for pay-for-performance use
cases but should not be used to implement fairness. Instead, use the
share
attribute to ensure equitable distribution of
I/O resources.
Parent topic: Administering the IORM Plan