
Table
4-41 (Page 2 of 2). Performance Statistics
Bytes
Description
32–35
Write sequential I/O operation hits. The number of sequential operations that had at least one write
command but did not cause any portion of a track to be staged from the disk subsystem to cache.
36–51
Reserved, for Cache Fast Write Statistics. Set to zeros.
52–55
Inhibit cache loading I/O operations. These bytes will be set to zeros because Internal Disk ignores
the Inhibit Cache Loading state of the Global Attributes. The counts with Inhibit Cache Loading will be
accumulated in the normal counters.
56–59
Bypass cache I/O operations. The number of operations that had at least one search, read or write
command. The Define Extent command specified bypass cache.
60–63
Sequential disk to cache transfer operations. The number of tracks transferred from the disk
subsystem to cache in anticipation of future sequential requests.
64–67
Disk to cache transfer operations. The number of tracks or partial tracks transferred from the disk
subsystem to cache excluding the count in bytes 60–63.
68–75
Reserved, set to zeros
76–79
Internal Disk RAID Fast Write normal I/O operations. The number of operations that had at least one
Locate Record with Write Intent or CKD Write command. If byte 2, bits 2-3 indicate that IDRFW is
deactivated, this field will be set to zeros.
80–83
Internal Disk RAID Fast Write sequential I/O operations. The number of operations that had at least
one write command. The Define Extent command specified sequential access. If byte 2, bits 2-3
indicate that IDRFW is deactivated, this field will be set to zeros.
84–93
Reserved, set to zeros
94–95
Subsystem identifier (SSID)
96–191
Reserved, set to zeros
Attention Messages
When the Perform Subsystem Function command has the order code Prepare for
Read Subsystem Data with byte 6 equal to X
'
03
'
, a 9-byte attention message is
returned. This suborder is provided for compatibility with other subsystems of the
3990 family. Internal Disk has no attention messages defined so the 9 bytes that
are returned have a fixed format and relatively fixed content that is shown in
Table 4-42.
Table
4-42. Attention Message Format
Bytes
Description
0–1
Message length, set to X
'
0009
'
.
2
Set to X
'
00
'
meaning no messages with this message identifier.
3
Reserved, set to zero.
4–7
Message Identifier. These bytes are set to the same message identifier value
that was received in bytes 8-11 of the Prepare for Read Subsystem Data that
preceded.
8
Reserved, set to zero.
Chapter 4. Command Descriptions
4-141
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