Veritas Storage Foundation 5.1 SP1: Storage and Availability Management for Oracle (5900-1504, April 2011)

Veritas NetBackup also makes use of Storage Checkpoints to provide a very
efficient Oracle backup mechanism.
About Storage Rollbacks
Each Storage Checkpoint is a consistent, point-in-time image of a file system, and
Storage Rollback is the restore facility for these on-disk backups. Storage Rollback
rolls back changed blocks contained in a Storage Checkpoint into the primary file
system for faster database restoration.
Storage Checkpoints and Storage Rollback process
A Storage Checkpoint is a disk and I/O efficient snapshot technology for creating
a "clone" of a currently mounted file system (the primary file system). Like a
snapshot file system, a Storage Checkpoint appears as an exact image of the
snapped file system at the time the Storage Checkpoint was made. However, unlike
a snapshot file system that uses separate disk space, all Storage Checkpoints share
the same free space pool where the primary file system resides.
Note: A Storage Checkpoint can be mounted as read only or read-write, allowing
access to the files as if it were a regular file system. A Storage Checkpoint is created
using the dbed_ckptcreate command.
Initially, a Storage Checkpoint contains no data. The Storage Checkpoint only
contains the inode list and the block map of the primary fileset. This block map
points to the actual data on the primary file system. Because only the inode list
and block map are required and no data is copied, creating a Storage Checkpoint
takes only a few seconds and very little space.
A Storage Checkpoint initially satisfies read requests by finding the data on the
primary file system, using its block map copy, and returning the data to the
requesting process. When a write operation changes a data block in the primary
file system, the old data is first copied to the Storage Checkpoint, and then the
primary file system is updated with the new data. The Storage Checkpoint
maintains the exact view of the primary file system at the time the Storage
Checkpoint was taken. Subsequent writes to block n on the primary file system
do not result in additional copies to the Storage Checkpoint because the old data
only needs to be saved once. As data blocks are changed on the primary file system,
the Storage Checkpoint gradually fills with the original data copied from the
primary file system, and less and less of the block map in the Storage Checkpoint
points back to blocks on the primary file system.
Using Database Storage Checkpoints and Storage Rollback
Using Storage Checkpoints and Storage Rollback for backup and restore
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