The LSS internally uses a hierarchical map to track the physical locations of all serial elements in the store. It also maintains information about the current utilisation of all the segments.
All this information is itself written to the root block or the log, but only during a check point.
A check point is performed at the following times
A recovery scan is performed when the store is opened and it was found that it had not previously been closed gracefully. In that case it has to scan all segments in the end of the log since the last check point. This allows it to recover all committed transactions and roll back any uncommitted transactions.
The maximum time for the recovery scan is bounded by the time taken to read the segments at the end of the log since the last check point. The time to read 128 segments only takes a few seconds on a modern hard-disk.