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Storing Change Detection Information for CMS Backups

When defining the full backup job template file, the CA VM:Backup system administrator can set one of the following for change detection during CMS backups:

Date

CA VM:Backup stores file status table (FST) attributes (for example, date, size, and record format) for files in a file-level detail catalog. When creating a domain-level detail catalog, CA VM:Backup stores certain minidisk attributes in the catalog. Date is the default option.

With Date, only the FST information is stored in the catalog. In most cases, comparing the FST information of CMS files is sufficient to detect a change.

Hash

CA VM:Backup uses a hash value to determine whether the contents of a file or minidisk have changed.

If CA VM:Backup is creating file-level catalogs, CA VM:Backup computes a hash value of the contents of each file backed up along with its FST attributes and stores the values in the catalog.

If CA VM:Backup is creating domain-level catalogs, CA VM:Backup computes a hash value of the contents of each minidisk backed up and stores the values in the catalog.

Use Hash if you use non-CMS access methods that do not update file status table (FST) information when modifying files or minidisks. Hash requires more CPU and I/O resources than Date.