Standby components in a hot standby system are constantly being synchronized with the master component. The log entries that the master component writes to the log area are redone in the standby component automatically.
The dataset of a standby component always corresponds, albeit with a slight time delay, to the dataset of the master component. You use the special database parameter HS_DELAY_TIME to configure this time delay.
Unlike standby components, with standby instances log backups are only imported periodically.
The synchronization of standby components with the master component is triggered by the system at specific times. The master component regularly informs the standby components (special database parameter HY_SYNC_INTERVAL) of the position up to which new log entries have been written. This enables modifications that have been made since the last synchronization to be redone. The standby components report back to the master component, telling it the point up to which they have finished reading the log. The standby components then redo the log entries up to a certain point in time (HS_DELAY_TIME.)
The master component and the standby components use the same database parameter. When a new standby component is set up, it is given an exact copy of the parameter used by the master component. Any modifications to the parameter are always made to the master component and passed on to all the standby components automatically.