5.1.3.7 Tips for Managing Interdatabase Resource Plans

Note the following information when creating and managing interdatabase resource plans.

• If Oracle Exadata is only hosting one database, then an interdatabase plan is not needed.
• If an interdatabase plan is not specified, then all databases receive an equal allocation.
• If only one database is mapped to the OTHER directive and all other databases have an explicit directive, then Oracle Exadata System Software uses the database resource plan of that database to determine how the allocation of the OTHER database is redistributed among the consumer groups in that database.
• If multiple databases are mapped to the OTHER directive, then Oracle Exadata System Software does not use Oracle Database Resource Manager for these databases. All of the I/O requests are treated the same.
• For share-based plans, each database gets its own directive even when it is not explicitly named in the plan. Oracle Exadata System Software uses the database resource plan of the database to determine how the allocation is to be distributed between the consumer groups in the database.

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

  By itself, the DB_UNIQUE_NAME value is not case-sensitive. However, IORM may not work correctly when multiple instances of the same Oracle RAC database use inconsistent cases for DB_UNIQUE_NAME (for example, PROD and prod). Therefore, ensure that the DB_UNIQUE_NAME value is case-consistent across each Oracle RAC database.

  If no value is specified, the DB_UNIQUE_NAME value is derived from DB_NAME. In that case, ensure that the DB_NAME value is case-consistent across the Oracle RAC database.

• If you have databases with the same DB_UNIQUE_NAME but associated with 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 when specifying directives.

• Cache limits in an interdatabase IORM plan directive constrain the settings in any corresponding container database (CDB) plan.

  Consequently, if an interdatabase IORM plan directive specifies flashcachemin and flashcachesize settings for a database, then the PDB-specific memory_min quotas in the CDB plan represent fractions of the flashcachemin setting, and the PDB-specific memory_limit values represent fractions of the flashcachesize.

  However, if the interdatabase IORM plan directive specifies flashcachesize without flashcachemin, then the PDB-specific memory_min settings are ignored while the memory_limit settings continue to represent fractions of the flashcachesize.

  The same applies to the Exadata RDMA Memory Cache (XRMEM cache) regarding the relationship between the PDB-specific quotas in the CDB plan (memory_min and memory_limit) and the cache-specific settings in the interdatabase IORM plan (xrmemcachemin and xrmemcachesize).