Sql Dba Interview Questions And Answers For Experienced
Sql Dba Interview Questions And Answers For Experienced – One of the most popular features introduced in SQL Server 2012 is “AlwaysOn” which leverages the existing HA/DR features and provides additional features such as availability groups. This article is for SQL Server DBA who are preparing for interview, which includes basic and advanced level sql dba AlwaysOn Interview -1 interview questions.
The AlwaysOn Availability Groups feature is an advanced disaster recovery and backup solution that provides businesses with an alternative to data mirroring. Introduced in SQL Server 2012, AlwaysOn Availability Groups increase the availability of single-user databases for businesses. the
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Which fail together. Available units support a read-write primary data set and one to four parallel secondary data sets. If possible, there may be secondary data for read access and/or some backup operations.
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A repository for data sets, usable data, that have failed. Let’s consider a scenario where 3 sets of databases are linked based on application requirements. Now we need to configure HA for these 3 databases. If we choose a mirror, we should have a separate mirror setup for these 3 databases, as in AlwaysOn Availability Groups makes it easier to work by grouping all these 3 databases.
Data that belongs to existing groups. For each usable data set, the available group holds one read copy (the primary data) and one to four read-only copies (the secondary data).
Q What are the minimum data requirements to be part of an existing group?
Q. How many copies of read-only and read-only databases can be created in SQL Server 2012 and 2014?
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Available modules are owned by each available copy. The available mode specifies whether the primary replica waits to make transactions on the database until the secondary replica writes the given transaction log entry to disk (commits the log). AlwaysOn supports the following modes:
Asynchronous commit mode: The primary replica commits the transaction to the database without waiting for the commit from the secondary replica.
Synchronous method: The first copy does not perform the transaction on the database until it receives the confirmation (the log-transaction entry written on the second disk) from the second copy.
Replication that uses this method is known as asynchronously linked replication. In asynchronous commit mode, the first replica commits a transaction without waiting for confirmation while the second replica asynchronously commits the log. The asynchronous commit model minimizes the duration of secondary data transactions, but allows them to lag behind the primary data, which allows some data to be lost.
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Replicas that use this mode are known as sync replicas. In synchronous commit mode, before committing the transaction, the first commit synchronous replica waits for the second commit synchronous replica to verify that the log installation is complete. Synchronized commit mode ensures that once a given secondary database is linked to the primary database, committed transactions are fully protected. This security comes at the cost of increasing transaction latency.
The replica that is the primary database for read-write communication from the client is called the Primary Replica. Sends the transaction log entries for each primary database to the secondary replica.
A replica that holds a secondary copy of each existing database and can be a potential fallback target for an existing group. If possible, the secondary copy may support read-only access to the secondary database, may support backup of the secondary database.
An availability group listener is a server name that clients can connect to to access the database on the primary or secondary copy of the AlwaysOn availability group. Available group listeners direct incoming connections to the primary copy or to the read-only secondary copy.
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Active secondary capabilities of AlwaysOn Availability Groups include support for read-only access to one or more secondary replicas (secondary readable replicas). A read-only secondary copy provides read-only access to all secondary data. However, secondary readable data is not intended to be read-only. They are active. A given secondary database changes when changes to the corresponding primary database are applied to the secondary database.
We can have 2 synchronous copies, but we don’t have to use that either. We can run all subroutines asynchronously if desired
Yes. The active second can be used to transfer read-only requests from the first to the second instance in the existing group.
In the context of a session between a primary replica and a secondary replica, the primary and secondary roles can be switched in a process called failover. During failover, the target secondary replica moves to the primary role, becoming the new primary replica. New primary copies treat data on the Internet as primary data, and client applications can communicate with them. When the former first copy is available, it steps into the role of the second, and the second copy is gone. The previous primary data becomes the secondary data and data synchronization continues.
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There are three forms of deletion – automatic, manual and forced (with possible data loss). The form or form of failover supported by a given secondary copy depends on its mode.
Manual failover occurs after the data controller issues a failover command and causes the secondary configuration copy to move to the primary role (with secure data protection) and the primary copy to move to the second part. Manual failover requires both the target primary and secondary replicas to be in synchronization mode, and the secondary replica must be synchronized.
Automatic failover occurs in response to a failure that causes the secondary copy to fail over to the primary role (with reliable data protection). When the first copy is available, move to the second role. Automatic failover requires both the primary replica and the secondary target replica to run in synchronized execution mode, with the failover mode set to “Automatic”. Additionally, the secondary replica must be compliant, have WSFC quorum, and meet the requirements specified by the failover policy of the existing cluster.
SQL Server Failover Cluster Instances (FCIs) do not support automatic failover of availability clusters, so existing copies hosted by FCIs cannot be configured for manual failover.
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The only form of deletion is forced deletion (with possible data loss), often called forced deletion. Forced cancellation is considered a form of manual cancellation because it can only be initiated manually. Force failover is a disaster recovery option. This is the only possible form of failure when the target secondary copy does not match the primary copy.
Data administrators use the AlwaysOn Dashboard to get an at-a-glance view of the health of the AlwaysOn Availability Group and its copies and data in SQL Server 2012. Some of the common uses of the AlwaysOn Dashboard are:
We should be grateful to the authors who have provided good information on the subject of AlwaysOn from SQL Server 2012 and SQL Server 2014. Here is the list of top references:
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Businesses of all sizes and sectors rely on SQL developers to query data and perform data analysis; Finding the right expert or SQL team is an important step in being a data-driven business.
In order to get a good salary, it is important to organize a comprehensive recruitment process that identifies candidates with SQL experience and work ethic for your organization. Interviews can be tested in two areas, but since they require a lot of resources, we recommend that you use them after the first test of programming skills, such as:
Hiring a great SQL developer can be difficult if you are not a programming expert. Easily assess candidates’ skills with our online SQL test.
To get the most out of your interview process, consider using the SQL Server interview questions and sample answers below.
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We’ve divided the 50 questions into beginner, intermediate and advanced categories, so you can tailor the interview process to your company’s needs.
SQL Novice survey questions are best used for entry-level SQL Server roles, where candidates may not have professional SQL experience.
A relational database management system (RDBMS) refers to the software used to store, manage and retrieve data. Data is stored in tables and can be linked to other data based on shared information, hence the name “relational”.
SQL is a programming language used to perform data-related operations; Every RDBMS uses SQL as its standard programming language. In these databases, SQL allows users to create tables, update data, run queries and perform analyses.
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SQL is the programming language used in RDBMS, while MySQL is an example of RDBMS. MySQL was one of the first open source database systems on the market and is still popular today.
The CREATE TABLE command is used to create a new table
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