Channel Programs
Chapter 4. Count, Key, and Data Command Set
Figure 4-1 on page 4-2 is a summary of the count, key, and data (CKD) command set. This section of the manual contains a detailed description of each command and its use for 3330,3333,3340,3344,3350,3375, and 3380 operations. For illustration purposes, the CCW format for System/370 Mode, ECPS:VSE Mode, and 370-XA (Format 0) Mode is shown in the command examples.
Two commands, Define Extent and Locate Record, are used to notify the channel of the types of data transfer commands that will be executed and the limits in which they may operate. These commands replace the Seek, Set Sector,. Set File Mask, and Search commands used in other channel programs.
The data transfer commands, Write Update Data, Write Update Key and Data, and Write CKD Next Track, are provided for write operations on consecutive records following execution of the Define Extent and Locate commands.
Three additional commands, Set Path Group ID, Sense Path Group ID, and Suspend Multipath Reconnection, are used to support attachment of the 3380 Models AA4, A04, and B04 with dynamic path selection to the 3880 Models 2 and 3. These commands are also used to support attachment of the 3380 Models AE4, AD4, BE4, BD4, AJ4 and AK4 to the 3880 Model 3.
COMMAND CODE
MULTITRACK OFF MULTITRACK ON
HEXA-
HEXA-COMMAND DECIMAL BINARY DECIMAL BINARY
Control
Suspend Multipath Reconnection '5B' 0101 1011 Set Path Group Identifier (ID) '5B' 0101 1011
Unconditional Reserve '14' 0001 0100
Device Release '94' 1001 0100
Figure 4-1. Summary of Count, Key, and Data Command Set
4-2 IBM 3880 Storage Control Description
No-Operation
o
78 3132 3940 4748 63Command Data Address Flags Not Used Count
Code
00000011 Ignored X'03'
Function
(Decimal)
Used at the Must be
discretion of the nonzero to
programmer avoid program
check
The No-Operation (No-Op) command is used to maintain channel connection during I/O operations.
Chaining Requirements
Status
Description
None.
Channel end and device end are presented in initial status.
The No-Op command is processed as an immediate command. (Channel end is signaled immediately upon receipt of the command code.) It causes no action at the addressed device.
The No-Op command resets orientation information in the storage director.
Indiscriminate usage of the No-Op command within CCW chains may cause records or parts of records to be skipped. For example, a No-Op inserted between a Read Count command and a Read Data command may cause the data area of the following record to be read. Also, a No-Op inserted between a command that reads the data area of record N-l and a command that must process the count area of record N, may skip one or more records and process the count area of a subsequent record.
Recalibrate
o
78 3132 3940 4748 63Command Data Address Flags Not Used Count
Code
00010011 Ignored X'13'
Function
(Decimal)
Used at the Must be
discretion of the nonzero to
programmer avoid program
check
The Recalibrate command causes the addressed drive to seek to cylinder zero, head zero.
Chaining Requirements
Status
Description
None.
Initial status is normally zero. Channel end is presented as ending status and device end is presented after the access is positioned at cylinder zero, head zero.
The Recalibrate command is processed similarly to a seek command and the file mask must be set to allow seeks. A Recalibrate command following a Define Extent command will be executed only if cylinder zero is included in the defined extent.
4-4 IBM 3880 Storage Control Description
Seek
o
78 3132 3940 4748 63Command Code 00000111 X'07'
Function
Data Address Flags Not Used Count
(Decimal)
Specifies the main Used at the 6
storage location of the discretion of the
seek addr~ss programmer
The Seek command transfers the seek address from the channel to the storage director.
Chaining Requirements
Status
Description
If the 3380 AJ4/AK4 Attachment (Feature 3005) is installed, this command "1 must be preceded by a Seek, Seek Cylinder, Read IPL, Locate Record, or
I' ..
'Recalibrate command.
Initial status is normally zero. Channel end and device end are presented after the seek address has been transferred. See the description below for other status conditions.
The Seek command transfers the six-byte seek address from the channel to the storage director. The storage director saves the address to allow positioning of the access mechanism at a later time. If the seek address indicates that no access motion is required, the proper head is selected before channel end status and device end status are presented.
The storage director checks the seek address for validity (see the following chart). If the seek address is not valid, channel end, device end, and unit check with command reject are presented in ending status.
The format for the seek address is:
Byte 9 1 2 3 4 5
e e
C C H HIBM Confidential
3330 3380
Models Models Models AA4/A04/B04 AE4/BE4 AK4/BK4 Valid Seek Models Model 3340 3340 3344 3350 3375 AD4/BD4
Address** 1 or 2 11 (35 MB) (70 MB) (70 MB) AJ4/BJ4 Bytes 0, 1
and 4 must 0 0 0 0 0 0 0 0 0 0
be:
Bytes 2 and
3 are not 410 814 348* 697* 697* 559* 959* 885* 1770* 2655*
greater than:
Byte 5 is not
greater than: 18 18 11 11 11 29 11 14 14 14
CE cylinders 349 698 2,800 1,024 960 886 1771 2658
are: 699 through
2,804
SA cylinders 350 700 2,805 1,025 961 -3*** 1780 2667
and 2668 1781 2669
* Unless the file mask bit 5 is on. **All values are decimal.
*** File mask bit 5 must be on.
If access motion is required, it is not initiated until a Set Sector, read, search, write, Write Special Home Address, Read Special Home Address, or Space Count command is received in the same chain or until the CCW chain ends normally. If more than one Seek command is received in the CCW chain before access motion is initiated, only the last Seek command will cause access motion.
If the COW chain ends normally and the last Seek command has not been initiated, the storage director initiates the seek after disconnecting from the channel. If the device is addressed by another command before the seek is completed, device end is not generated, but busy status is presented.
The Seek command does not have to be preceded by another CCW in order to be executed. However, if a Define Extent or Set File Mask command has been issued, the file mask must be set to allow seeks. (See the Set File Mask section of this manual.) If preceded by a Define Extent command, the seek address must also be within the defined extent. (See the Define Extent command section of this manual.)
Execution of a Seek command resets track orientation information in the storage director.
4-6 IBM 3880 Storage Control Description