databases collection in config database have

docement
connect mongos
show dbs;
not have aaa database;

log file:
2015-12-11T23:59:07.379+0800 I NETWORK [initandlisten] connection accepted from #152741 (103 connections now open)
2015-12-11T23:59:07.502+0800 I NETWORK [conn234578] end connection 192.168.20.113:35936 (81 connections now open)
2015-12-11T23:59:07.503+0800 I NETWORK [initandlisten] connection accepted from 192.168.20.113:35940 #234582 (82 connections now open)
2015-12-11T23:59:08.081+0800 I SHARDING [conn15614] couldn't find database [aaa] in config db
2015-12-11T23:59:08.384+0800 I NETWORK [conn241020] end connection (1418 connections now open)
2015-12-11T23:59:08.385+0800 I NETWORK [initandlisten] connection accepted from #241025 (1419 connections now open)
2015-12-11T23:59:08.755+0800 I NETWORK [conn132274] end connection (901 connections now open)
2015-12-11T23:59:08.755+0800 I NETWORK [initandlisten] connection accepted from #132278 (902 connections now open)

I tried to manually drop the aaa database, and connect to the mongos exect db.runCommand ("flushRouterConfig"); Over a period of time and the same question.