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25. Now, anybody will be able to connect to my SQL DM for MySQL server and retrieve details about MySQL servers.
A: Of course not! The SQL DM for MySQL authentication system will ensure that only those people that should have access have.
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26. I have the same server registered twice. Metrics are reported different. Why?
A: For every registered server SQL DM for MySQL collects data independently. That is also the case when a server has been registered twice. Even if they were registered at the same time and even if the chosen sample interval is the same too, the connection and the server will have some latency and data will not be retrieved simultaneously. For that reason SQL DM for MySQL may (or rather will) retrieve and store slightly different values for each connection. This is most visible in the 'Delta' timeframe and least visible in the 'Current/all' timeframe. For GROUPING with 'History/Trends' the difference for each GROUP will depend on the selected grouping interval. Due to laws of statistics the difference will be less the longer the time interval (theoretically/statistically they will converge more and more the closer time interval and/or the no. of samples comes to infinity). Practically, you will rarely need more than around 20 samples in a GROUP for the difference to be negligible.
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27. Will it affect the performance of a server if SQL DM for MySQL connects to it?
A: It will practically not on real 'live' servers. The queries sent by SQL DM for MySQL use almost no resources. We do not query data stored on disk and what we do query is stored in memory on the server. However if you are testing SQL DM for MySQL using a server instance that does almost nothing else and if you retrieve data at very short intervals the impact of SQL DM for MySQL may be slightly observable. The special Processlist feature (unique) may take a little more resources if there are lots of processes/client threads running. But SQL DM for MySQL only sends queries related to this when the corresponding SQL DM for MySQL client interface (the SQL DM for MySQL 'processlist' page) is open. Switching to another page or closing the browser will stop sending the queries populating the SQL DM for MySQL processlist.
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28. Is it possible to avoid that SQL DM for MySQL itself influences certain counters reported?
A: SQL DM for MySQL is a client. When it connects the MySQL server will start a connection thread. And that connection will be reported by SQL DM for MySQL. That cannot be avoided. The processlist feature has an option to 'filter out' SQL DM for MySQL connection - as well as other connections from other clients if you want - using a simple SELECT statement.
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