The updating algorithm of the first-level cache has been described in Algorithm 1. Q1 contains the
continuous data from the source system, which are those that will be loaded into the first-level cache.
Meanwhile, these data will be inserted into the queue Q2, convenient for data updating in the secondlevel
cache. In this way, data has backups in Q2, and then the data in C1 can be directly removed when it
is refreshed, which can reduce operations on the cache.