5.1.3.1 About Interdatabase IORM Plan Directives

Interdatabase plan directives are specified using the DB_UNIQUE_NAME of the database as the identifier.

When using allocation-based resource management, each directive consists of an allocation amount and a level from 1 to 8, which is similar to a database resource plan. For a given plan, the total allocations for any level must be less than or equal to 100 percent. An interdatabase plan differs from a database resource plan in that it cannot contain subplans and only contains I/O resource directives.

Share-based plans use a relative share instead of percentage allocations and levels. These plans are simpler to implement, but as effective as percentage allocations. Each database is given a share value which is an integer between 1 and 32. The sum of the shares can be up to 32768. Share-based plans support up to 1024 directives within the interdatabase plan. For example, if a critical database, FINANCE, has 4 shares, and a low-priority database, REPORTING, has 1 share, then during periods of resource contention the FINANCE database is four times more likely to issue I/Os compared to the REPORTING database.

Oracle Exadata System Software uses the interdatabase plan and database resource plans together to allocate I/O resources.

• First, the interdatabase plan allocates the I/O resources to individual databases.
• Next, the database resource plan for each database allocates the I/O resources to consumer groups. If a database does not have an active database resource plan, all user I/Os are treated the same. Background I/Os are automatically prioritized relative to the user I/Os based on their importance.

As a best practice, you should create a directive for each database that shares the storage. This is done automatically for shared-based plans, but not for allocation-based plans. To ensure that any database without an explicit directive can be managed with percentage allocation plans, create an allocation named OTHER. Databases without explicit directives are managed using the allocation of the OTHER group directive.

Each database that is not explicitly mapped in a share-based plan gets the default share of 1. However, share-based plans can use the DEFAULT directive to specify the default values for the different IORM attributes.

If you have databases with the same DB_UNIQUE_NAME in different Oracle ASM clusters, then starting with Oracle Exadata System Software release 19.1.0, you can use the asmcluster attribute to uniquely identify each database in the interdatabase plan.