HP XP P9500 Storage - Manual (Page 137)

Table 28 State table for Continuous Access Synchronous vs. Continuous Access Asynchronous (continued)
Transfer data via
ESCON Writing control on Cnt Ac-S async volume Description Storage system
internal state RAID
Manager
state
Response Writing data Continuous Access
Asynchronous Continuous
Access
Synchronous
Sidefile Wait until under
threshold Via Sidefile Over
Threshold
Sidefile Usual Normal Deleting from PAIR
using [pairsplit -S] N/A Deleting
Sidefile Usual Via Bitmap Using
[pairsplit ] Suspending
from PAIR N/A Suspending
Timeout of
over
threshold
None Usual Via Bitmap Same PSUS PSUS PSUS
None Usual Via Bitmap Timeout Over Threshold None PFUS
None Usual Via Bitmap Same (link down, etc) PSUE PSUE PSUE
None Usual Via Bitmap Same PDUB PDUB PDUB
* If the host has more write I/Os in COPY state, then host write I/Os are delayed until there is enough space in the sidefile.
Legend:
Bitmap: Host write data is managed via a cylinder BITMAP of delta data.
Normal: Host write data is not managed by BITMAP or sidefile.
Usual: Host side writing response is not delayed.
HWM (High Water Mark): Sidefile quantity is over 30% of cache storage.
Continuous Access Asynchronous/Continuous Access Journal error state
In the case of an ESCON or fibre-channel (FC) failure, the S-VOL FIFO queue is missing a data
block that was transferred from the P-VOL FIFO queue. The RCU waits to store the next sequenced
data block in the S-VOL FIFO queue until the Continuous Access Asynchronous copy pending
timeout occurs (defined using Continuous Access Synchronous). If the timeout occurs during this
waiting state, the pair status changes from PAIR to PSUE, and non-sequenced data blocks are
managed by the S-VOL bitmap. The missing data block can be recovered using the pairresync
command, which merges the S-VOL bitmap with the P-VOL bitmap.
Figure 56 (page 137) shows
this situation on the secondary side.
Figure 56 Continuous Access Asynchronous suspension condition
Continuous Access Synchronous, Business Copy, and Continuous Access Journal operations 137