Requesting Dynamic Cache Management

You can use storage class attributes to control the selection of volumes supported by storage controls that use dynamic cache management. Once the data set is allocated on a volume, storage class attributes determine how the services of the storage control are used to satisfy the data set's performance requirements.

The bias attributes, Sequential and Direct, interact with the Millisecond Response (MSR) attributes, Sequential and Direct, to determine if a data set requires the services of a cache-capable storage control. If the Direct or Sequential Millisecond Response attribute's value can only be satisfied by a cache-capable storage control, the Direct and Sequential bias attributes are evaluated to see if the data set is primarily read (R) or written (W). SMS attempts to allocate data sets on the device that most closely matches the MSR and BIAS that you choose.

If the data set is allocated on a cache-capable 3990 storage control, dynamic cache management handles must-cache and may-cache data sets differently, based on the use of the 3990 resources.

Figure 1 shows the ISMF panel that describes storage performance requirements for data sets that must be cached with the DASD fast write services of a cache-capable 3990 storage control.

Figure 1. Storage Class Define Panel, Page 1 of 2

  Panel  Utilities  Scroll  Help                                              
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                              STORAGE CLASS DEFINE              Page 1 of 2   
Command ===>                                                                  
                                                                              
SCDS Name . . . . . : USER6.TEST.SCDS                                         
Storage Class Name  : SC1                                                     
To DEFINE Storage Class, Specify:                                             
  Description ==>                                                             
              ==>                                                             
  Performance Objectives                                                      
   Direct Millisecond Response . . . .             (1 to 999 or blank)        
   Direct Bias . . . . . . . . . . . .             (R, W or blank)            
   Sequential Millisecond Response . .             (1 to 999 or blank)        
   Sequential Bias . . . . . . . . . .             (R, W or blank)            
   Initial Access Response Seconds . .             (0 to 9999 or blank)       
   Sustained Data Rate (MB/sec)  . . .             (0 to 999 or blank)        
   OAM Sublevel  . . . . . . . . . . .             (1, 2 or blank)            
  Availability . . . . . . . . . . . . N           (C, P ,S or N)             
  Accessibility  . . . . . . . . . . . N           (C, P ,S or N)             
   Backup  . . . . . . . . . . . . . .             (Y, N or Blank)            
   Versioning  . . . . . . . . . . . .             (Y, N or Blank)            
Use ENTER to Perform Verification; Use DOWN Command to View next Page;        
Use HELP Command for Help; Use END Command to Save and Exit; CANCEL to Exit.