Oracle Database Exadata Cloud Service provides an interface for Exadata I/O Resource Management (IORM) that enables prioritization of I/O resources amongst different databases.
Exadata IORM allows workloads and databases to share I/O resources automatically according to user-defined policies. Exadata Cloud Service provides a simple interface to enable IORM across multiple databases.
This facility uses a system of shares that are allocated amongst all of the databases that run on the Exadata system. Each database is assigned a share value between 1 and 32, with 1 being the lowest share, and 32 being the highest share. The share value represents the relative importance of each database.
Every database is automatically assigned a default share value of 1. In this state, every database receives an even share of the available I/O resources. Increasing the share value for a specific database increases its relative importance, and consequently decreases the amount of I/O available for all of the other databases.
For example, on an Exadata system with four databases, one share is allocated to each database by default. This ensures that each database is allocated 1 out of every 4 I/Os when the system becomes loaded enough for IORM to intervene. If the share value for one database is changed to 2, the total number of shares increases to 5. Now, when IORM is required, the database with a share value of 2 is allocated 2 out of every 5 I/Os, while the databases with a share value of 1 are each allocated 1 out of every 5 I/Os.
In addition to prioritizing access to I/O resources, the share value also prioritizes access to Exadata flash storage resources. The available flash storage space is divided up according to the total number of allocated shares, and each database is allocated an amount of space according to its share value. Consequently, databases with a larger share value are given access to proportionally more flash storage space.
Adjusting IORM share values for databases
To adjust the IORM share values for databases:
Open the Oracle Database Cloud Service console.
For detailed instructions, see Accessing the My Services Dashboard and the Oracle Database Cloud Service Console.
Locate a database deployment that you want to adjust the IORM share for, and from the associated action menu () select Update Exadata IORM.
The Exadata I/O Resource Management dialog is displayed.
In the Exadata I/O Resource Management dialog, use the Shares fields to specify the share value for each database deployment on the corresponding Exadata Cloud Service instance.
When you are satisfied, click Save to implement the settings. Alternatively, click Cancel to leave the dialog without updating any of the share values.
Implementing a custom IORM policy
In addition to prioritizing between databases, Exadata IORM can manage resources across different workload categories, both within a single database and across multiple databases, by using a custom IORM policy. To implement a custom IORM policy, you must submit a Service Request to Oracle Support. When you submit the Service Request, you must specify the custom IORM policy that you wish to implement by providing the
ALTER IORMPLAN command to apply to the Exadata Storage Servers. You will be notified through the Service Request when the policy is enabled.
For details about submitting the Service Request see How to Request Service Configuration for Oracle Database Exadata Cloud Service. Also, see the Oracle Exadata Storage Server Software User's Guide for details about the
ALTER IORMPLAN command.