_version is an internal column of ovsdb tables, which is not part of the ovsdb schema, but when plugin reads schema from the switch it also sends this column as a part of the schema. This columns gets updated every time any change happen to any row in the table (e.g updating statistics column ). This generate huge amount of update from the switch to the plugin and that generate unnecessary load at the plugin. This severely impact the scalability and performance of the plugin.