504 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
10.3.10 FlashCopy mapping events
In this section, we describe the events that modify the states of a FlashCopy. We also
describe the mapping events that are listed in Table 10-3.
Table 10-3 Mapping events
Overview of a FlashCopy sequence of events:
The following tasks show the FlashCopy sequence:
1. Associate the source data set with a target location (one or more source and target
volumes).
2. Create a FlashCopy mapping for each source volume to the corresponding target
volume. The target volume must be equal in size to the source volume.
3. Discontinue access to the target (application dependent).
4. Prepare (pre-trigger) the FlashCopy:
a. Flush the cache for the source.
b. Discard the cache for the target.
5. Start (trigger) the FlashCopy:
a. Pause I/O (briefly) on the source.
b. Resume I/O on the source.
c. Start I/O on the target.
Mapping event Description
Create A FlashCopy mapping is created between the specified source volume
and the specified target volume. The operation fails if any one of the
following conditions is true:
The source volume is a member of 256 FlashCopy mappings.
The node has insufficient bitmap memory.
The source and target volumes are different sizes.
Prepare The prestartfcmap or prestartfcconsistgrp command is directed to
a Consistency Group for FlashCopy mappings that are members of a
normal Consistency Group or to the mapping name for FlashCopy
mappings that are stand-alone mappings. The prestartfcmap or
prestartfcconsistgrp command places the FlashCopy mapping into
the Preparing state.
The prestartfcmap or prestartfcconsistgrp command can corrupt
any data that was on the target volume because cached writes are
discarded. Even if the FlashCopy mapping is never started, the data
from the target might be changed logically during the act of preparing
to start the FlashCopy mapping.
Flush done The FlashCopy mapping automatically moves from the preparing
state to the prepared state after all cached data for the source is
flushed and all cached data for the target is no longer valid.
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