HP 3000 Manuals HP 3000 Manuals
Storing Files Online Online backup should be used to store those critical applications that need to be available at all times. At the time online backup is started, all files must be closed for a brief period (approximately five minutes) while they are attached to a shadow logging system. After the backup process begins, users can open their files for read/write/purge access. The shadow logging subsystem maintains the original state of the files as they appeared when the online backup began. If an attached file is modified, the before image of the portion (block) of the file being modified is saved in a log file. After the store process has written the attached file to the backup media, it requests the logging information from the shadow subsystem and appends the logged data, if any, to the end of the data file.
NOTE The logging operation will fail if there is not enough disk space available. In this event, files needing log space are not stored.
If an attached file is purged during the online backup, the system logically removes the file, but does not physically remove it until it has been stored. Therefore, the backup reflects the state of the system at the time STORE was initiated. [REV BEG]
NOTE Online backup is optional and is available only if you are using TurboSTORE/XL II with On-Line Backup (product numbers 36388A and 36398A).
[REV END] Performing Online Backup Heavily modified files should be stored first. This is accomplished by specifying these files first in the STORE command fileset list. By storing these files first, you reduce the system overhead and the amount of logging information written to the backup media (refer to "Online Backup Tapes" in appendix C for the online backup tape format). When online backup begins, the shadow subsystem assigns each file in the store fileset to a log file created on the same volume where the file resides. Actual logging activity does not take place unless the file is modified after the attach phase. The amount of log space required is directly proportional to the amount of modifications performed against the attached file. Therefore, the more modifications made to an attached file, the more log space required. In the worst case, the maximum amount of log space required equals the sum of the space required for all of the files being stored. By storing the heavily modified files first, you reduce the amount of logging space required. Reducing the amount of logging data written to the backup media will also reduce the time required to restore the files. [REV BEG] As each piece of backup media is filled, logging is disabled for the files that were stored on that media.[REV END] Use the ONLINE parameter of STORE to perform an online backup. Before the STORE process is initiated, you must warn the users to close all files to ensure that the files are both physically and logically consistent. For example, the following message can be sent: WARN @S;ONLINE BACKUP WILL BEGIN IN TEN MINUTES. PLEASE CLOSE YOUR FILES. [REV BEG] Begin the online backup by specifying the ONLINE parameter with the STORE command. For example, the following illustrates the STORE command entry for an online backup to tape. STORE @.@.@;*T;DIRECTORY;ONVS=MPEXL_SYSTEM_VOLUME_SET,NV1;ONLINE The following illustrates the STORE command entry for an online backup to a DASS device. STORE @.@.@;;MOSET=(101);NAME=DAILY.D24SEPT.TIGER;DIRECTORY;& ONVS=MPEXL_SYSTEM_VOLUME_SET,NV1;ONLINE [REV END] When online backup begins, all files not currently open for write are attached to a log handler known as the shadow subsystem. Once the attach phase is complete, STORE issues the following message to the console. FILES LOCKED BY ONLINE STORE ARE NOW FREE FOR READ/WRITE/PURGE After you receive the above message, the users are allowed read, write and purge access to the attached files. Send your users a message telling them they may resume their applications. For example, WARN @S;ONLINE BACKUP HAS BEGUN. YOU MAY NOW RESUME YOUR APPLICATIONS. If any files were still open at the time you started online backup, you will receive the following message: ! NOT STORED: FILE OPEN FOR WRITE AT ATTACH where ! is replaced by the actual file name(s). During the RESTORE process, the log file is used to reconstruct the original contents of the files; that is, the way they appeared at the moment they were attached during online backup.
NOTE The ONLINE option cannot be specified with the SPLITVS or TRANSPORT options.
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