DB2 buffer pool "4096" has no more pages

Yesterday, we found a customer´s database in a strange state. Whenever doing some of the more bandwith-demanding ETL operations, we were presented with the annoying error message:

Operation could not be performed, because buffer pool has no more pages left.

After some internet search, we found out that these ids belong to buffer pools (so called hidden, for most serious cases under-dimensioned buffer pools - kind of replacement tires) that are not officially assigned to the relevant tablespaces, but that get used once the memory manager cannot start the actually assigned pools, e.g., due to memory shortage.

The database finally had to be restarted (online activation of the buffer pools did not work) in order to get the state back to normal.