@Override public void dropCatalog(String catalogName) throws NoSuchObjectException, MetaException {
    rawStore.dropCatalog(catalogName);

    // in case of event based cache update, cache will not be updated for catalog.
    if (!canUseEvents) {
      catalogName = catalogName.toLowerCase();
      sharedCache.removeCatalogFromCache(catalogName);
    }
  }
This starts a background thread, which initially populates the SharedCache and later
periodically gets updates from the metastore db

@param conf
@param runOnlyOnce
@param shouldRunPrewarm
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/cache/CachedStore.java