If you have an IBM® 3990 Storage
Control with cache with at least one SMS volume attached, you can
display cache statistics, hit ratio, and DASD Fast Write bypasses,
by issuing the following command:
D SMS,CACHE
An example
of the generated output appears below.
Figure 1. Displaying Cache and DASD Fast Write Information IGD002I 09:28:38 DISPLAY SMS 411
SSID DEVS READ WRITE HIT RATIO FW BYPASSES
0002 32 80 60 68% 62
0004 14 92 100 76% 30
000E 20 84 100 84% 44
0011 08 100 100 92% 16
001C 08 100 100 86% 24
***************************** LEGEND *****************************
SSID THE SUBSYSTEM IDENTIFIER OF THE IBM 3990 STORAGE CONTROL
MODEL 3 TO WHICH THE INFORMATION APPLIES
DEVS THE NUMBER OF SMS-MANAGED DEVICES ATTACHED TO THE IBM 3990
STORAGE CONTROL MODEL 3 WITH THIS SSID
READ THE PERCENTAGE OF CYLINDERS FOR WHICH DYNAMIC CACHING IS
PERMITTED
WRITE THE PERCENTAGE OF CYLINDERS FOR WHICH DYNAMIC DASD FAST
WRITE IS PERMITTED
HIT RATIO THE READ HIT RATIO THAT IS ACHIEVED BY THE IBM 3990 STORAGE
CONTROL MODEL 3 WITH THIS SSID
FW BYPASSES THE NUMBER DASD FAST WRITES PER MINUTE THAT ARE EXECUTED
DIRECTLY WITH DASD BECAUSE OF MVS OVER-COMMITMENT
Exception: The read and write percentages
are displayed as N/A if the subsystem has the extended platform available.
Since the enhanced dynamic cache management algorithm is used, the
percentages are no longer valid.