CICS File Availability 24/7 (CFA)
CFA provides VSAM file reorganization/backup while the file is open to CICS. A small service window reduces the time VSAM files are unavailable to CICS, providing virtually 24/7 File Availability. During the file reorganization process, a DASD backup file is created, which can be moved to tape or the cloud as required.
The problem with traditional VSAM file reorganization/backup
With traditional VSAM file reorganization/backup, the file must be closed to online access before the reorganization/backup process begins to ensure the new file content matches the original.
If the reorganization/backup is for a large file, this process can take several minutes to hours. The file cannot be re-opened until the copy, delete, define, and repro are complete (the file is unavailable for use).
How CICS File Availability 24/7 solves the problem
CFA creates a copy of the existing VSAM file while keeping it open and available for updates in CICS. After the copy is complete, any changes made to the existing VSAM file during the copy process are applied to the new VSAM file using the CICS forward recovery log data set. After updates are applied, the existing VSAM file is closed, which opens the service window.
While the service window is open, a CICS file exit suspends any temporary transactions attempting to use the file. A second pass through the CICS forward recovery log data set ensures that the existing and new VSAM files are identical. Next, the current file is renamed with a predefined “old” suffix and the newly reorganized file to the existing VSAM file name. After the rename, the reorganized VSAM file is opened, the CICS file exit is disabled, and any suspended transaction is released, thus closing the service window.
This small service window is usually seconds … not minutes or hours!
The original (.old) file is the backup file on DASD, which can be moved to tape or the cloud as required.
CFA eliminates the restrictions with IBM's Backup While Open (BWO) option, making it a better choice for VSAM file backup.
Does CICS File Availability 24/7 work with RLS VSAM files?
CFA uses a process similar to RLS files, except RLS files must be QUIESCED and closed during the service window rename process. After the rename is complete, RLS files are UNQUIESCED and then opened.
What if the VSAM file uses associations (Path or Alternate Index)?
New associations are defined and created for the new VSAM file as part of the copy process.
For additional information on how CICS File Availability 24/7 can help you