About the Storage Checkpoint facility and NetBackup for DB2
The BLI backup methodology uses the Storage Checkpoint facility in the Veritas File System (VxFS). This facility is available through the Storage Foundation for DB2.
The VxFS Storage Checkpoint facility keeps track of the file blocks modified by the database since the last backup. NetBackup with BLI backup leverages this facility to back up only changed blocks for an incremental backup. The entire volume or file is not backed up.
VxFS Storage Checkpoint is a disk-efficient and I/O-efficient snapshot of file systems. A Storage Checkpoint provides a consistent, stable view of a file system at the instant when the file system was snapped or checkpointed. Instead of making a physically separate copy of the file system, a Storage Checkpoint tracks changed file system blocks. Disk space is saved and I/O overhead is significantly reduced.
Because the changed blocks are tracked, the VxFS Storage Checkpoint enables BLI backups. VxFS Storage Checkpoint facility provides a consistent view of file systems, which allows BLI backup to freeze the database image during database backups.
The Storage Checkpoint operation is similar to the snapshot file system mechanism. However, the Storage Checkpoint persists after a system restart which is unlike a snapshot. Also, the Storage Checkpoint operation is totally transparent to backup administrators. The Checkpoint image is managed and available only through NetBackup or through the VxDBA utility for database backup available with the Veritas Storage Foundation.
For more information on Storage Checkpoints, see the Veritas Storage Foundation Administrator's Guide.
You can take a Storage Checkpoint while the database is online or offline. To take a Storage Checkpoint while the database is online, you must enable archive logging. During the creation of the Storage Checkpoint, all tablespaces are placed in backup mode.