刪除mongo分片collection失敗

在中止balancer以後，備份整個分片庫，而後啓用balancer，刪除分片集合並重建。遇到如下報錯：

mongos> db.businessInfo.drop();
2016-08-14T09:06:58.324+0800 E QUERY    Error: drop failed: {
"code" : 13331,
"ok" : 0,
"errmsg" : "exception: collection's metadata is undergoing changes. Please try again."
}
    at Error (<anonymous>)
    at DBCollection.drop (src/mongo/shell/collection.js:620:15)
    at (shell):1:12 at src/mongo/shell/collection.js:620

理了一下邏輯，應該先drop sharding collection而後再啓用balancer.