Fable
The library cut long scrolls into small page boxes that could be borrowed and returned
The royal library kept the long scrolls that readers were currently reading. The old method was for each reader to occupy an entire row of shelves—even if only a few sections were used, contiguous space had to be reserved.
When there were few readers, no one minded. Later, as long scrolls increased, many shelves clearly had empty gaps but could not fit a new reader's entire scroll because the space was not contiguous. The librarian said the shelves were full, but in reality the space was fragmented everywhere.
The director first expanded the library, then limited each person to reading only a few volumes. The expansion was expensive, and the limit hurt researchers who truly needed long materials, but the problem did not disappear.
Someone separated the short scrolls from the long scrolls, but where a long scroll had been read to, when the next page would be needed, and which pages were no longer required still left the shelves with more and more fragments.
A book restorer proposed splitting the long scroll into small page boxes of equal size. Readers would no longer occupy a continuous shelf, but would take only a few page boxes; the boxes could be stored separately, and a catalog would connect the order.
When a reader finishes a section, the page box is returned; when a new reader needs space, they can take any empty page box without waiting for an entire shelf to empty. The library can suddenly serve more people. The long scroll remains complete, and readers can still read in order; it is only the underlying storage that has changed from one continuous large block to paginated management.
The director understood that congestion comes not only from insufficient capacity, but also from capacity that cannot be used once it is fragmented. Managing fragmentation is often more valuable than blindly buying more bookshelves.
Later, when the library received long-scroll researchers, it first checked the page-box pool and the catalog, rather than first looking for a whole row of empty shelves. True efficiency came from turning memory space into small blocks that could be allocated and reclaimed. Later the librarians found that the catalog itself was also crucial. If the page boxes were scattered in different places and the catalog recorded the order incorrectly, the long scroll the reader read would be broken; if pages were not returned after use, the page-box pool would still run dry. So every page borrow, return, and swap had to be logged. Paging made space flexible, and logging kept flexibility from turning into chaos. The library relied on both together to serve ever-longer scrolls. Later, during peak storage hours, the librarians first reclaimed already-read page boxes, then took on new readers. Space was no longer occupied once and for all, and long-scroll service had elasticity. Only when page boxes can flow will long scrolls not clog the stacks. Only when fragments are managed does capacity return. Only when the catalog is reliable is paging reliable.