Nonstop Database, HiRDB Version 9 UAP Development Guide
Depending on the order in which the sequence generator storage RDAREA and the RDAREA storing the table that uses the sequence generator are backed up, there might be duplicate or missing sequence numbers after the database has been recovered.
If you back up the sequence generator storage RDAREA and the RDAREA storing the table that uses the sequence generator at the same time, there will be no duplicated or missing sequence numbers.
Figure 4-76 Backing up the sequence generator storage RDAREA and the RDAREA storing the table that uses the sequence generator at the same time
There might be duplicated sequence numbers. The following figure provides an example.
Figure 4-77 When the sequence generator is backed up before the table that uses the sequence generator
Sequence numbers might be duplicated.
Sequence generators cannot be used with the replication facility (HiRDB Dataextractor and HiRDB Datareplicator). If sequence generators with the same name are used at the source and the target, sequence numbers might be duplicated because the source sequence generator's current value cannot be inherited to the target.
There might be missing sequence numbers. The following figure provides an example.
Figure 4-78 When the table that uses the sequence generator is backed up before the sequence generator
If you wish to restore the database to a desired synchronization point after a backup was made or to the most recent synchronization point before a failure, you must restore the backup files and system log files or unload log file. In this case, as many sequence numbers might be missing as the value you set for the log output interval when you defined the sequence generator. The following figure provides an example.
Figure 4-79 When logs are used for recovery
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