Hitachi TrueCopy for IBM z/OS User and Reference Guide (T5211-96001, June 2007)

About TrueCopy for z/OS Operations 2-19
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
TrueCopy for z/OS Async Recordset Operations
The TCzA recordsets contain the TCzA M-VOL updates and the associated
control information, including the time-stamp of the M-VOL update, which
enables the RCU to maintain update consistency of the TCzA R-VOLs. TCzA
recordset operations include:
• Creating and storing recordsets at the MCU
• Sending recordsets to the RCU
• Storing recordsets at the RCU
• Selecting and settling recordsets at the RCU
• Types of recordsets
• Inflow control for sidefiles.
Creating and Storing Recordsets at the MCU
When an MCU performs an update (host-requested write I/O) on a TCzA M-
VOL, the MCU creates a TCzA recordset which contains:
the updated record,
time-stamp information, sequence number, record location (device, cylinder,
track, record number), and record length. The TCzA recordsets are queued in
the cache storage of the MCU and sent to the RCU independent of host I/O
processes. The RCU utilizes the time-stamp and sequence number information
in the recordsets to update the R-VOL(s) in the same order as the M-VOL(s).
The time-stamp information is acquired from the (MVS) host’s I/O time-stamp
function. This time stamp provides a protective measure for write-dependent
applications and minimizes recovery time in the event of a disaster. The
sequence number indicates the number of recordsets that the MCU has
created for each consistency group. The recordset information, except for the
updated records, is stored and queued in an area of cache known as sidefile
cache.