Wednesday, April 19, 2017
SQL Server 2017 becomes the first commercial RDMS with built-in AI support
Monday, August 29, 2016
Powershell supports Linux
Thursday, July 28, 2016
Microsoft releases CU #1 for SQL Server 2016
Microsoft released their latest flagship database product, Microsoft SQL Server 2016 on June 1st 2016. After 2 months, now Microsoft announced the release of CU #1 which contains fixes for 146 issues across different categories of the product.
The CU1 has 146 hotfixes in 10 different categories as stated above. The highest no.of hotfixes are for the SQL Service.
You can download the CU1 by using the below link.
Cumulative Update 1 for SQL Server 2016
Cheers.
Saturday, January 18, 2014
SQL Server 2014 changes ACID behavior
Any database professional know what it means by ACID. They are some golden properties of relational systems.
A – Atomicity
C – Consistency
I - Isolation
D – Durability
SQL Server supports ACID properties fully until SQL Server 2012. In SQL Server 2014 (still in CTP level) DBA has the option to control the D of ACID. Till SQL Server 2012, the log records need to be flushed to the disk before a transaction can be declared committed. However in SQL Server 2014, this statement is not 100% valid with the introduction of new feature called “delayed durability”.
With this new option, SQL Server transactions can be either fully durable or delayed durable. BOL states;
“Fully durable transaction commits are synchronous and report a COMMIT as successful and return control to the client only after the log records for the transaction are written to disk. Delayed durable transaction commits are asynchronous and report a COMMIT as successful before the log records for the transaction are written to disk. Hardening transaction log entries to disk is required for a transaction to be durable. Delayed durable transactions become durable when the transaction log entries are flushed to disk.”
As it obvious thing, the delayed durability comes with a cost that, there could be a data loss in the event like fail over. The advantages of this option are, reduce contention and increase throughput.
Use of delayed durability option is not suitable for all the cases. This can not be used in situations where you cant tolerate a data loss.
Delayed durability option can be applied at Database level, Atomic code block level and Commit level.
It is worth to be considered why Microsoft changed the ACID behavior after 22 years of SQL Server history. I believe this is an response to the highly volatile database technology market which we are seeing today, specially with the widely use of NoSQL technologies. NoSQL technologies are using “BASE” (Basically Available, Soft state, Eventual Consistency) against the ACID in relation systems. With the introduction of BASE the NoSQL vendors claim that the support for big data and huge performance gain in OLTP as opposed to the relational databases.
Finally, I believe it is a great option and DBAs will like the new feature. However, SQL Server 2014 is still in CTP which means it is subjected to change in future releases, sometimes this could be completely removed.
For more details, How to: Control Transaction Durability
Tuesday, July 10, 2012
Replication framework between relational database and document oriented (NOSQL) database
I started a discussion on this in LinkedIn mongoDB user group and received couple of valuable comments. Many thanks for those who given the comments.
You can see them here.
Friday, March 2, 2012
VLDBs backup in few seconds
Friday, February 17, 2012
Pearson Lanka DBA team at SS SLUG
How to interpret Disk Latency
I was analyzing IO stats in one of our SQL Servers and noticed that IO latency (Read / Write) are very high. As a rule of thumb, we know tha...
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This can happen due to many factors like lack of indexes, out of dates statistics, if it returns a large number of records, etc. I observed...
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I was analyzing IO stats in one of our SQL Servers and noticed that IO latency (Read / Write) are very high. As a rule of thumb, we know tha...
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This post is for SQL Server Database Administrators who have find difficulty in some situations when identifying slow running queries. The D...