How to Repair Suspect Database in SQL Server with DBCC CHECKDB

Sometimes when connecting to the database, the database becomes inaccessible and you will get the following error message:

error message 945

The error message indicates that the database is in SUSPECT mode. Continue reading

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DBA Interview Question# Can we create a snapshot for MSDB system database?

DBA Interview Question# Can we create a snapshot for MSDB system database?

Recently I have been approached for one of my technical friend regarding the snapshot for system databases i.e. Master, Model. MSDB & TempDB whether possible or not.

As per Microsoft recommendation, snapshot is prohibited for Master, Model & TempDB so the question is here what about the MSDB snapshot, is it possible to generate?

Can we create a snapshot for MSDB system database?

Here I am sharing the details as an answer with you all after having  done a practical on it.

Answer:

The answer is yes, we can create the snapshot for MSDB system database.

MSDB

If we try to generate the snapshot for other system databases then we will get the error as below:

Model DB

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Trace Flags in SQL Server

Trace Flags in SQL Server

Traces

Trace flags plays an important role in database administration. These are frequently used to diagnose performance issues or to debug stored procedures. For example trace flag 1222 is to detect the deadlock and returns the resources and types of locks pertaining in a deadlock

In SQL Server, there are three types of trace flags, query, session and global. Query trace flags are only active for the specific query. Session traces flags are active only for that particular session or connection. Global trace flags are set at the server level and are visible to every connection on the server.

There are several types of trace flags available. Here I’ll take mostly example of deadlock trace flags which is the most common for the DBA use.

Permissions

Requires membership in the sysadmin fixed server role.

Rules

1.

A global trace flag must be enabled globally, otherwise the trace flag has no effect. It is recommended to enable global trace flag at start up, by using the –T command line option. This ensures the trace flag remains active after a server restart.

The trace flag should be enabled with appropriate scope whether it is global, session or query scope. A trace flag which is enabled at the session level never affects another session, and the effect of the trace flag is lost when the SPID that opened the session logs out.

How to set Trace flags on or off

1.

Using DBCC TRACEON & DBCC TRACEOFF

E.g. DBCC TRACEON (1222, -1)

The effect of enabling a global trace flag with DBCC TRACEON is lost on server restart.

To turn off a global trace flag, use

DBCC TRACEOFF with the -1 argument

DBCC TRACEOFF (1222, -1)

2.

-T (T stands as Trace flag) start up option

The –T startup option enables a trace flag globally. We can’t enable a session-level trace flag by using a startup option. This ensures the trace flag remains active after a server restart. This can be done via SQL Server configuration manager.

Note: Here we can set the trace flag in Startup Parameters as “-T1222”.

How to start\stop traces:

Dbcc traceon (trace no) – for current session

Dbcc traceon (traceno, -1) – to enable globally

Dbcc traceon (no1, no2, -1) – enable multiple traces globally

How to check trace status:

Dbcc tracestatus

Dbcc tracestatus (-1) – display all globally enabled flags

Dbcc tracestatus () – display all trace flags enabled for current session

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SQL Server High Availability and Database Recovery Model Relationship

Recovery model

There are four types of high availability options available in Microsoft SQL server. All the options are different from each other. For example, Log shipping, Mirroring and Always On works on database level while Replication works on database objects level. The databases involved in these high availability feature must have a fixed type of recovery models else it is not possible to configure these options. Here I am briefing about the recovery models of the database which are involved in high availability.

HA & Recovery Models

How to check the recovery model of a database?

Method 1:  sp_helpdb

Method 2: select name as [Database Name], recovery_model_desc as [Recovery Model] from sys.databases

How to change the recovery model of a database?

Method: T-SQL

Alter database database name set recovery full/bulk logged/simple

E.g.

alter database Mirza set recovery full

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DBA Daily Tasks

sql-server DBA Daily Tasks

This blog is especially for those people who are preparing to be a Database Administrators or who have just started their career in the database administration field.

As a production DBA, we are supposed to perform several tasks on the servers on a daily basis to make and keep the server and database healthy. Monitoring the server is a key to safe our databases from any risk which may occurs in future. I am mentioning here only basic but very important tasks.

  1. Health Check of critical Servers
  2. Alerts from the servers needs to be acknowledged
  3. All the tickets to be checked and follow up
  4. Emails follow up
  5. Attend the scheduled client call
  6. Project work follow up
  7. Document the database environment

1.Health Check

Health checkup of the serves includes several checks which we need to perform on the critical servers and prepare a complete report. Here we need to check for database status, disk space utilization, CPU and Memory utilization, all the backups’ jobs and other maintenance jobs, error logs etc.

Important T-SQL commands can be used:

  1. Sp_helpdb
  2. Sp_spaceused
  3. Xp_fixeddrives

2. Alerts Acknowledgement

Any alert receives from the server via database mail or through any tool, we need to acknowledge and need to work upon them.

  1. Ticket Follow up

Mostly all companies use some ticketing system to get the database related issue \ task through it. All the tickets come with a SLA (service level agreement) which needs to be adhere and finish it within stipulated time frame.

  1. Email Follow up

Sometimes we get email from the client which contains a long list of database related talks which we need to work upon. So we have to follow-up on all emails and keep the status up to date without any fail.

  1. Call Attendance

For different project work related call with the clients, are scheduled and invitation goes to every team member. Therefore it is necessary for the DBA to attend the call and make the points clear on any ongoing work\ issue.

  1. Project Work Follow-up

Apart from daily routine work, project work also there which takes time and team do work side by side in parallel e.g. any database migration, AOAG setup on new servers, Server setup etc. Therefore we have to sync our self with the project work and keep updated on every task which is going on. By this way a new DBA can enhance his\her knowledge as well.

  1. Documentation

DBA performs several task in a single day and sometimes the task is a strange and new to DBA. We need to document all task either new or any project work to make every member of the team be on the same platform and make the life easy.

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Introduction to Microsoft Azure

Microsoft Azure

Microsoft Azure is an open, flexible, enterprise-grade cloud computing platform. Azure was announced in October 2008 and released on February 1, 2010.

It provides

Software as a service (SaaS)

Platform as a service (PaaS)

Infrastructure as a service (IaaS)

Why is it different from other cloud computing?

  1. Microsoft cloud is global, trusted and hybrid.
  2. 42 Azure regions, more than any other cloud provider
  3. 90% of fortune 500 companies use the Microsoft cloud.
  4. 1,20,000 new Azure customer subscriptions per month
  5. 62 compliance offerings more than any other cloud provider

Microsoft Azure – Popular Services\Products

  1. Virtual Machines
  2. App Services
  3. SQL Databases
  4. Storage
  5. Cloud Services
  6. Azure Cosmos DB
  7. Azure Active Directory
  8. Backup
  9. SQL Data Warehouse
  10. Traffic Manager
  11. Azure Database for MySQL
  12. Azure Databases for PostgreSQL

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How to add and remove a database to an availability group in Always On

How to add and remove a database to an availability group in Always On

Rule:

  1. Connect to the server instance that hosts the primary replica.
  2. Use the T-SQL statement as below
  3. After you add a database to an availability group, you need to configure the corresponding secondary database on each server instance that hosts a secondary replica.

To add a database to an availability group

Syntax:

ALTER AVAILABILITY GROUP group_name ADD DATABASE database_name [,…n]

E.g.

Group Name = MirzaAG

Database Name= Mirza (Existing database in the instance)

T-SQL

ALTER AVAILABILITY GROUP MirzaAG ADD DATABASE Mirza

How to start data synchronization after adding a database to an Always On availability group

  1. For each new primary replica, secondary databases must be prepared on the server instances that host the secondary replicas. Then each of these secondary databases must be manually joined to the availability group.
  2. If the file paths are identical on every server instance that hosts a replica for an availability group then the data synchronization starts automatically else we have to manually to do it as below.

 To start data synchronization manually follow these steps:

  1. Restore current backups of each primary database and its transaction log (using RESTORE WITH NORECOVERY). You can use either of the following alternative approaches:
    • Manually restore a recent database backup of the primary database using RESTORE WITH NORECOVERY, and then restore each subsequent log backup using RESTORE WITH NORECOVERY. Perform this restore sequence on every server instance that hosts a secondary replica for the availability group.
    • As soon as possible, join each newly prepared secondary database to the availability group.

 To remove an availability database,

Rule:

  1. This task is supported only on primary replicas. You must be connected to the server instance that hosts the primary replica.
  1. Requires ALTER AVAILABILITY GROUP permission on the availability group,
  2. Use the Alter Availability Group T-SQL statement

Syntax:

ALTER AVAILABILITY GROUP group_name REMOVE DATABASE availability_database_name

e.g.  Group_Name = MirzaAG

Database Name= Mirza

T-SQL

 Alter availability group MirzaAG remove database Mirza

Summary:

Removing an availability database from its availability group ends data synchronization between the former primary database and the corresponding secondary databases. The former primary database remains online. Every corresponding secondary database is placed in the RESTORING state.

At this point there are alternative ways of dealing with a removed secondary database:

  • If you no longer need a given secondary database, you can drop it.
  • If you want to access a removed secondary database after it has been removed from the availability group, you can recover the database. However, if you recover a removed secondary database, two divergent, independent databases that have the same name are online. You must make sure that clients can access only one of them, typically the most recent primary database.

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