Saving a database online

HSMS (operands SAVE-OPTIONS=*PARAMETERS(SAVE-ONLINE-FILES=YES)) or ARCHIVE (operands PARAM OLS=YES ) can be used to save the UDS/SQL database files while the database is being processed and updated by DBH.

Prerequisites for an online database backup

• You must have declared that the database can be saved online using the utility routine BMEND (ENABLE-ONLINE-COPY statement) before starting database operation.

• AFIM logging (After Image Logging) must be activated for the database since a consistent database state is reflected only by the online backup in conjunction with the ALOG file(s) generated during the save operation. The online backup itself is usually inconsistent unless administrative measures are taken to ensure that the database is consistent at the start of the backup operation and that no changes are made during the entire period of the backup.
  To establish a consistent state on the basis of an online backup, you should first restore the backup to disk before using the utility routine BMEND to update it using the associated ALOG file(s) (UPDATE-DATABASE statement).

Creating online backups

To create online backups of databases or individual realms, you should always use the corresponding HSMS or ARCHIVE statements.

CAUTION!

When COPY-FILE is used to generate an online copy, the system does not check whether "online backup capability" is enabled for the database concerned. In this case you must therefore ensure yourself that AFIM logging is enabled so that the online copy can be made consistent later by applying the changes.

When you start a modifying UDS utility routine, you must make sure that any online backup operations started beforehand for the database to be processed are terminated, otherwise the online copy might be unusable.

It is not permissible to generate online copies while modifying utility routines are running.

Online backup capability of a database copy

Whether or not a database can be backed up online is recorded both in the UDS administration data and in the database files’ DMS catalog entries. When a database is copied, either with COPY-FILE or with HSMS/ARCHIVE, the specifications concerning the database’s online backup capability may be lost depending on the parameters that are used. As a result, before using a database copy of an original for which the online backup capability was active, you must ensure that this property is consistent, e.g. by running the utility routine BMEND again with the ENABLE-ONLINE-COPY statement.