7.7.1.7.7 limit Attribute

Purpose

The limit attribute specifies the maximum flash I/O utilization limit.

Syntax

 ALTER IORMPLAN 
   dbplan=(( name=db_name, ... limit=number ... ) ... )

 ALTER IORMPLAN 
   clusterplan=(( name=cluster_name, ... limit=number ... ) ... )

Usage Notes

• limit: Specifies the maximum flash I/O utilization limit as a percentage of the available resources. The attribute applies only to I/O on flash devices, which includes flash-based grid disks and Exadata Smart Flash Cache.

  Valid values are 1 to 100. If a limit is specified, then excess capacity is never used by the associated database or cluster. Consequently, it is possible for flash devices to run below full capacity when limits are specified.

  Note:

  Specifying low limit values can have a significant performance impact and is generally not advisable.

• Resource management using limits is ideal for pay-for-performance use cases but should not be used to implement fairness. Instead, use the share attribute to ensure equitable distribution of I/O resources.

Example 7-45 Using the limit Attribute with a Database Plan

CellCLI> ALTER IORMPLAN                                        -
         dbplan=((name=db1, limit=40),                         -
                 (name=db2, limit=40),                         -
                 (name=DEFAULT, limit=20))