OLTP
DSS
A
B
ESTABLISH
C SPLIT
i
ii
D ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREOLTP
DSS
A
B
ESTABLISH
C SPLIT
i
ii
D ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREIBM Storage Subsystem Library "IBM 3990
Strage Control Reference Fifth Edition", September 1991B
ESTABLISH
B
ESTABLISH
ii
ii
IBM Storage Subsystem Library "IBM 3990 Strage ControlReference Fifth Edition", September 1991
Dual Copy Operations
The 3990 Model 3 can have dual copy volumes. Dual copy allows the user to have two identical setsof data on two different DASD volumes within the same subsystem.When a host program establishes dual copy and identifies two DASD volumes as a duplex pair, the3990 model 3 maintains two identical copies of a volume, independent of application-level hostprogramming. See establish Duplex Pair X'12' on page 159 for information on how to specify aprimary and a secondary device.
3990 3
DASD
DASD
3990 3
X'12'
Dual copy has four device states:
Duplex: Has two devices, the primary and the secondary. These devices make up the duplex pair. Onlythe primary device is functional to the host system.All commands that address the secondary device are rejected, except for the following:Suspended Duplex: A state caused by one of two events: 1 a host program requests the state of theduplex pair be changed to suspended, or 2 the 3990 Model 3 is unable to synchronize the contents ofthe two devices, and has stopped duplicate writes.
2 3990 3
Establish Duplex Pair X'12' The order makes a duplex pair from the devices that theparameters specify as the primary and secondary devices. It can also restore a duplex pair from asuspended duplex pair or replace a failed duplex device with another device.When possible it alsoreturns the device to the original channel address. X'12'6-7 Determine if a copy is required to establish the duplex pair. The values are:
00 Device are syncronized the data is identical , do not copy to establish the deplex pair.
01 Copy from the primary to the secondary device to establish the duplex pair. The entire volume willbe copied to syncronize the two DASD devices. 6-7:
DASD
A
B
C
i
ii
D
MT MT
0004 0005
ESTABLISH SPLIT
ESTABLISH REESTABLISH
RESTORE INCREMENTAL RESTORE
A
B
C
D
SPLIT
ii
SPLIT
ii
OLTP
DSS
A
B
ESTABLISH
C SPLIT
ii
D ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREIBM Storage Subsystem Library "IBM 3990 Strage ControlReference Fifth Edition", September 1991
ESTABLISH
ESTABLISH
A
B
B
parallel concurrent
independent concurrent
B
C i
C ii
D
B
OLTP
OLTP
OLTP
ESTABLISH
BCV
C i
SPLIT
SPLIT
SPLIT
BCV
NR
SPLIT
D
B
SPLIT
C
SPLIT
C ii
SPLIT
ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREESTABLISH REESTABLISH
RESTORE INCREMENTAL RESTORE
ESTABLISH REESTABLISH RESTORE
INCREMENTAL RESTORE
1 3
B
1 SPLIT i
ii
SPLIT
C i
SPLIT
B
B
B
C i C ii
B
1 2
SPLIT
C
SPLIT
ESTABLISH REESTABLISH
RESTORE INCREMENTAL RESTORE
ESTABLISH
ESTABLISH
DASD
DASD
DASD
OLTP
B
C i C ii D
B
parallel operation
parallel processing
concurrent processing
concurrent processing
B
B
D
OS
D
B ESTABLISH
C i
D
ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREC i
D
C i
C i
NR
BCV
SPLIT
SPLIT
SPLIT
SPLIT
C i
C i
B
C i D
A
B
B
DASD 3990 3
B
B
C
SPLIT
SPLIT
SPLIT
RESTORE
RESTORE BCV
BCV
BCV
RESTORE
BCV SPLIT
SPLIT
SPLIT
ESTABLISH REESTABLISH RESTORE INCREMENTAL RESTOREESTABLISH ESTABLISH
2 3
B
B
DASD
DASD
CE DE
DASD 0017
DASD
DASD
DASD
SPLIT
C SPLIT i
C in response to a second command: i detaching the second data storagefacility from the first data storage facility independently of operations in response to thefirst application C
i
SPLIT
MT
MT
OLTP
RDF
RDF
RDF
RDF
C i
OS
B
B
D
0019 0023
D
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