Choosing the type of snapshot
The following table describes three major objectives and the optimal snapshot type for each one.
Choosing the best snapshot type
Objective | Best snapshot type | Benefits |
|---|---|---|
Minimize outage time | Software snapshot | Software snapshots (where the utility actually copies the data) are the fastest and most economical method. They use extended memory to save page preimages, and only use memory for pages updated during the snapshot. |
Maximize success rate | Hardware snapshots | Hardware snapshots can potentially use whatever hardware is available (mirroring, data set snaps) to establish a point-in-time image that the utility copies. They relieve the resource demand for software snapshots. Hardware snapshots can fall back to software snapshots if the hardware attempt fails for any reason. |
Minimize recovery time | Instant Snapshots | Instant Snapshots duplicate data sets without any program copying data. They can duplicate back to the original data set (restore for recovery). They support SHRLEVEL CHANGE for Db2 to allow for an outage-free backup. |
The following table indicates the relative order of each snapshot type for each of the objectives.
Objective | First choice | Second choice | Third choice |
|---|---|---|---|
Minimize recovery time | Instant | Software | Hardware |
Minimize outages | Software | Hardware | Instant |
Maximize success rate | Hardware | Software | Instant |