There are three resource plans - intradatabase, interdatabase, and category - that Exadata uses to allocate I/O resources among databases and consumer groups. The intradatabase plan manages resources within each database, while the interdatabase plan allocates resources among databases. The category plan allocates resources based on the type of work. These plans work together, first selecting a category, then a database using the interdatabase plan, and finally a consumer group using the intradatabase plan. The percentage of resources allocated to each consumer group is calculated based on the allocations in each plan level. IORM ensures consumer groups within the same category and database maintain the same ratio of allocations, even if the absolute allocations change.

1. I/O Resource for Exadata Databases
---------------------------------------------------------There are three plans - category, interdatabase, and intradatabase which
are used together by Exadata to allocate I/O resources.
Intradatabase Resource Plan: To create an intradatabase resource plan
Database resource management is configured within each database, using
Database Resource Manager.
This is the only IORM feature that is needed If only one database is using
Exadata.
Interdatabase Resource Plan: this plan specifies how resources are
allocated among multiple databases for each cell.
Category Resource Plan : Exadata is hosting multiple databases and to
allocate resources primarily by the category of the work being done.
IORM plan : Both the interdatabase plan and the category plan which are
defined in a cell object known as the IORM plan.
I/O Resource Management Plan explained :
i. First the category plan is used to allocate resources among the categories.
ii. After selected a category, the interdatabase plan is used to select a
database. The selected databases must have consumer groups with the
selected category.
iii. Finally, the selected database’s intradatabase plan is used to select one
of its consumer groups.
The percentage of resource allocation represents the probability of making a
selection at each level which is measured by below formula:
Pcgn = cgn / sum(catcgs) * db% * cat%
where:
• Pcgn is the probability of selecting consumer group n.
• cgn is the resource allocation for consumer group n.
• sum(catcgs) is the sum of the resource allocations for all consumer
groups in the same category as consumer group n and on the same
database as consumer group n.
• db% is the database allocation percentage in the interdatabase plan.
• cat% is the category allocation percentage in the category plan.

2. Consumer Group (CG) names are abbreviated to CG1, CG2, and so on.
IORM is concerned with the ratio of consumer group allocations within each
category and database.
IORM allocation for Database A on Batch Category
-----------------------------------------------------------------CG1: (15/(15+10)*70%*40%)= 16.8%;
CG2: (10/(15+10)*70%*40%)= 11.2%;
IORM allocation for Database A on Interactive Category
------------------------------------------------------------------------CG3: (35/(35+40)*70%*60%)= 19.6%;
CG4: (40/(35+40)*70%*60%)= 22.4%;
IORM allocation for Database B on Batch Category
-----------------------------------------------------------------CG5: (22/(22+18)*30%*40%)= 6.6%;
CG6: (18/(22+18)*30%*40%)= 5.4%;
IORM allocation for Database B on Interactive Category
------------------------------------------------------------------------CG7: (15/(15+45)*30%*60%)= 4.5%;
CG8: (45/(15+45)*30%*60%)= 13.5%;

3. IORM is related with the ratio of consumer group allocations within each
category and database.
Findings:
i. The value of Consumer Groups receives same of I/O resources from
IORM if the intradatabase plan allocations are doubled. For example if we
doubled for CG1 to 30% and CG2 to 20% respectively.
CG1: (30/(30+20)*70%*40%)= 16.8%;
CG2: (20/(30+20)*70%*40%)= 11.2%;
This is because the allocation to CG1 remains 50% greater than the
allocation to CG2.
ii. Again for the ratio of consumer group allocations within each category
and database similar allocation through IORM.
Ex:
Between CG1 and CG3 and between CG6 and CG8
For database A
-------------------CG3 belongs to the higher priority category (60%) than CG1 ( 40%)
CG3 much larger intradatabase plan allocation (35% versus 15%).
For database B
------------------CG8 belongs to the higher priority category (60%) than CG6 ( 40%)
CG8 much larger intradatabase plan allocation (45% versus 18%).
Exadata cells use the IORM plan in conjunction with the DBRM plans
propagated by the databases to allocate I/O resources.