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Both InnoDB and PostgreSQL - as well as many other databases - use a technique called multi-version concurrency control (MVCC) to provide transaction isolation: transactions should not see the work of other, uncommitted transactions. MVCC means that, when a row is updated, the database stores both the old and new versions of the row.

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Thursday, March 1, 2012

DNS QUERY TIMEOUT ON LINUX CLIENT

Hi all, here i have come with a situation, when we have multiple DNS, basically Nameserver entry in resolve.conf at client, and sometimes we also face dam slow resolves in queries, this is may also due to DNS server issue, may be DNS has gone away or some other issues that is making it slow to resolve queries.By default, linux client attempts 3 times to Nameserver for queries. Here it make the process slow.
So what we can do, is to set timeout in resolve.conf, this will help client to choose another Nameserver for AnswersHere we go:

Edit the file resolve.conf:

# vi /etc/resolve.conf

nameserver 192.168.1.71
nameserver 192.168.1.72
nameserver 192.168.1.73
nameserver 192.168.1.74
options         timeout:1
options         attempts:1

Here you can see, i have set options value in file.

options timeout:1  --> will tell client to skip this server, if there is delay in Answer
options attempts:1 --> will tell client to do just single attempt per server

Now you can check the difference.

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