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The host perceives this as an ordinary read from the R1 device, although the data
was read from the R2 device acting as if it was a local copy.
HYPERMAX OS
Arrays running HYPERMAX OS cannot service SRDF/A read I/Os if DSE has been
invoked to temporarily place some data on disk.
Read operations from R2 devices
Reading data from R2 devices directly from a host connected to the R2 is not
recommended, because:
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SRDF/S relies on the application’s ability to determine if the data image is the
most current. The array at the R2 side may not yet know that data currently in
transmission on the SRDF links has been sent.
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If the remote host reads data from the R2 device while a write I/O is in
transmission on the SRDF links, the host will not be reading the most current data.
EMC strongly recommends that you allow the remote host to read data from the R2
devices while in Read Only mode only when:
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Related applications on the production host are stopped.
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The SRDF writes to the R2 devices are blocked due to a temporary suspension/
split of the SRDF relationship.
Remote replication solutions
136 Product Guide VMAX 100K, VMAX 200K, VMAX 400K with HYPERMAX OS
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