| FlashCopy® |
IBM®
(EMC, HDS, or any vendor that supports FlashCopy emulation) |
With FlashCopy emulation, IMS can be across several vendors
DASD. Technology to drive FlashCopy in IMS Recovery Expert is
very fast. (Very small amount of time to issue the FlashCopy commands)
DFSMSdss can be used to drive fast-replication data set restore
of IMS object data sets. Users can specify target ranges so
there is no need to update a profile when IMS expands to new
volumes. Does not require SMS. |
Log suspend required. Older EMC FlashCopy emulation
(pre 72 microcode) is somewhat slower. HDS FC emulation is quite
slow also elongating the log suspend time. Not an incremental
copy - all tracks are copied in the background on each backup.
Fast database restore (through DFSMSdss) will use host based IO
(slow copy) if the background copy is not complete. Volumes must
be clipped and brought online to offload to tape. |
| TimeFinder Mirror (BCVs) |
EMC |
Uses EMC Consistency. No log suspend needed. Backup is
completely done and usable at split time. Restores can be done
right away. Snap data set can be used for almost instantaneous
restore of IMS database data sets. Does not require SMS. Fast
database restore can be performed through Snap data set without
clipping and bringing the volumes online. |
Two phase backup. Establish BCV (wait for sync), then split
BCV to make backup. If you have N generations
of backup disks, you only get N-1 backups on
disk because one generation is always mirroring the source
volumes. IMS must be completely on EMC DASD. When IMS expands to
new volumes, profile must be updated to add new BCV target
units. Volumes must be clipped and brought online to offload to
tape. |
| TimeFinder Clone (Full volume snap to target volume) |
EMC |
Uses EMC Consistency. No log suspend needed. Can be performed
in phases (phased snap) so performance implications to source
volumes can be timed and mitigated. Snap is differential; only
changed tracks are copied since the last backup. Snap data set
can be used for almost instantaneous restore of IMS database
data sets. Users can specify target ranges so there is no need
to update a profile when IMS expands to new volumes. Does not
require SMS. Fast database restore can be performed through Snap
data set without clipping and bringing the volumes
online. |
Full system restore must wait until background copy is
complete. Fast database restore (Snap data set) must wait until
background copy is also complete. IMS system must be completely
on EMC DASD. |
| TimeFinder Snap (Virtual Device Snap - VDEV) (V2.2) |
EMC |
Uses EMC Consistency. No log suspend. Space efficient snap.
Does not need a full backup volume for each source IMS volume.
Many backup points can be saved on fast-replication disk. Uses a
"SAVE POOL" to store changes to source device after the backup
is taken. Users can specify target ranges so there is no need to
update a profile when IMS expands to new volumes. Does not
require SMS. |
Must monitor the save pool to ensure it does not fill up.
Also, a true disk backup never exists; only the changed tracks
are stored in the save pool. Cannot perform a Snap data set
restore from this type of backup. IMS system must be completely
on EMC DASD. |