5.2.3.2 Using Share-Based Resource Management

A share value represents the relative importance of each entity.

With share-based resource allocation, a higher share value implies higher priority and more access to the I/O resources. For example, a database with a share value of 2 gets twice the resource allocation of a database with a share value of 1.

Valid share values are 1 to 32, with 1 being the lowest share, and 32 being the highest share. The sum of all share values in a plan cannot be greater than 32768.

Share-based resource allocation is the recommended method for the interdatabase plan (dbplan). For the cluster plan (clusterplan), share-based resource allocation is the only option.

The following example illustrates how to use share-based resource management in an interdatabase plan. Consider four databases sharing the same Oracle Exadata Storage Server resources. The four databases are:

• A critical OLTP production database, named PROD
• A test database, named PROD_TEST
• A development database, named PROD_DEV
• A data warehouse database, named DW

An OLTP production database typically issues small I/O requests, and low latency for these requests is the critical requirement. A data warehouse issues large numbers of large I/O requests and is more sensitive to the I/O throughput than the latency of each individual I/O request. Without any I/O resource management, the large number of I/O requests issued by the DW database could overwhelm the storage subsystem and increase the latency of the I/O requests issued by the PROD database. Additionally, the I/O requests issued by the test and development databases, PROD_TEST and PROD_DEV, could adversely affect the performance of the PROD and the DW databases.

To ensure a reasonable distribution of I/O resources, you can define a share-based interdatabase plan as follows:

CellCLI> ALTER IORMPLAN                                    -
         dbplan=((name=prod, share=16),                    -
                 (name=dw, share=4),                       -
                 (name=prod_test, share=2),                -
                 (name=DEFAULT, share=1))

By using the example interdatabase plan, the critical OLTP database (PROD) gets priority when there is contention for I/O resources. Specifically, the I/O share for PROD is 4 times greater than DW, 8 times greater than PROD_TEST, and a 16 times greater that the default share that is assigned to PROD_DEV.

At any time, you change the share allocations to adjust the relative priorities.