What is SQL Server restore and recovery?
SQL Server restore and recovery supports restoring data from backups of a whole database, a data file, or a data page, as follows: The database (a complete database restore) The whole database is restored and recovered, and the database is offline for the duration of the restore and recovery operations. The data file (a file restore)
How to recover a SQL Server database from a failure?
To recover a SQL Server database from a failure, a database administrator has to restore a set of SQL Server backups in a logically correct and meaningful restore sequence. SQL Server restore and recovery supports restoring data from backups of a whole database, a data file, or a data page, as follows: The database (a complete database restore)
What is fast recovery in SQL Server?
To maximize the availability of databases in an enterpirse environment, SQL Server Enterprise Edition can bring a database online after the Redo Phase, while the Undo Phase is still executing. This is known as Fast Recovery. The restore operations that are available for a database depend on its recovery model.
What is a recovery database (RDB)?
The database and log files can be restored to any disk location. Exchange analyzes the restored data and replays the transaction logs to bring the databases up to date, and then a recovery database can be configured to point to already recovered database files. RDBs are different from standard mailbox databases in several respects:
What are the types of database recovery?
What Are the Types of Recovery? There are three basic types of recovery: instance recovery, crash recovery, and media recovery.
What are database recovery techniques?
The techniques used to recover the lost data due to system crash, transaction errors, viruses, catastrophic failure, incorrect commands execution etc. are database recovery techniques. So to prevent data loss recovery techniques based on deferred update and immediate update or backing up data can be used.
What is database backup and recovery?
Backup and recovery describes the process of creating and storing copies of data that can be used to protect organizations against data loss.
What is recovery process in SQL Server?
SQL Server restore and recovery supports restoring data from backups of a whole database, a data file, or a data page, as follows: The database (a complete database restore) The whole database is restored and recovered, and the database is offline for the duration of the restore and recovery operations.
What are the 3 recovery models?
Three recovery models exist: simple, full, and bulk-logged. Typically, a database uses the full recovery model or simple recovery model.
What are the three types of recovery?
Name the three types of recovery? Self-recovery, Like-recovery, and Dedicated-recovery.
What are the 3 levels of backup may be used in database recovery management?
Normal or Full Backups. When a normal or full backup runs on a selected drive, all the files on that drive are backed up. ... Incremental Backups. ... Differential Backups. ... Backup and Recovery Software for MSPs. ... All Your Backups in One Place.
What is backup file in database?
In this article A file backup contains all the data in one or more files (or filegroups). For more information about file backups, see Full File Backups (SQL Server) and Differential Backups (SQL Server).
What are the different system recovery options?
System Recovery Options contains the following tools available:Startup Repair. Startup Repair automatically scans your hard disk for errors and tries to fix the errors.System Restore. ... Complete PC Restore or System Image Recovery. ... Windows Memory Diagnostic Tool. ... Command Prompt.
What are the three phases of database recovery?
SQL Server database recovery consists of three phases: the analysis phase, the redo phase, and finally the undo phase.
What is crash recovery in DBMS?
Crash recovery is the process by which the database is moved back to a consistent and usable state. This is done by rolling back incomplete transactions and completing committed transactions that were still in memory when the crash occurred (Figure 1).
Which is not a recovery techniques in DBMS?
Two-phase commit is not a recovery technique Data recovery is the process of restoring data that has been lost, accidentally deleted, corrupted or made inaccessible.
What are the different methods of rest recovery one could use after exercising?
LifestyleSleep more. Sleep gives your muscles time to recover from exercise. ... Massage. Many athletes incorporate massage in their training to reduce muscle soreness. ... Compression garments. Wearing compression garments has become common among athletes over the past several decades. ... Contrast water therapy. ... Cryotherapy.
What is log based recovery techniques in DBMS?
Log-based recovery provides the facility to maintain or recover data if any failure may occur in the system. Log means sequence of records or data, each transaction DBMS creates a log in some stable storage device so that we easily recover data if any failure may occur.
What is recovery database?
A recovery database (RDB) is a special kind of mailbox database that allows you to mount a restored mailbox database and extract data from the restored database as part of a recovery operation. You can use the New-MailboxRestoreRequest cmdlet to extract data from an RDB. After extraction, the data can be exported to a folder or merged into an existing mailbox. RDBs enable you to recover data from a backup or copy of a database without disturbing user access to current data.
What is RDB recovery?
An RDB can be used to recover data in several situations, such as: Same server dial tone recovery: You can perform a recovery from an RDB after the original database has been restored from backup, as part of a dial tone recovery operation. Alternate server dial tone recovery: You can use an alternate server to host the dial tone database, ...
Can RDB be used as a backup?
An RDB can be used as a target for restore operations, but not backup operations.
Can Exchange Server restore data?
Microsoft Exchange Server supports the ability to restore data directly to a recovery database. Mounting the recover ed data as a recovery database allows the administrator to restore individual mailboxes or individual items in a mailbox. Restoring to a recovery database can be accomplished in two ways:
Can you recover a database on a server other than the original server?
Recovering a database on a server other than the original server for that database. If needed, you can then merge the recovered data back to the original server.
Is the original database in Active Directory?
The logical information about the original database and the mailboxes in that database remains intact and unchanged in Active Directory.
Can you restore multiple databases with RDBs?
RDBs are generally not designed for scenarios in which you have to restore entire servers, when you have to restore multiple databases, or when you're in an emergency situation that requires changing or rebuilding your Active Directory topology.
What is the log file used for recovery?
Recovery techniques are heavily dependent upon the existence of a special file known as a system log. It contains information about the start and end of each transaction and any updates which occur in the transaction. The log keeps track of all transaction operations that affect the values of database items.
What is a full database backup?
Full database backup – In this full database including data and database, Meta information needed to restore the whole database, including full-text catalogs are backed up in a predefined time series.
What is the process of updating a database before it reaches its commit point?
Immediate update – In the immediate update, the database may be updated by some operations of a transaction before the transaction reaches its commit point. However, these operations are recorded in a log on disk before they are applied to the database, making recovery still possible. If a transaction fails to reach its commit point, the effect of its operation must be undone i.e. the transaction must be rolled back hence we require both undo and redo. This technique is known as undo/redo algorithm.
What happens if a transaction fails before reaching its commit point?
If a transaction fails before reaching its commit point, it will not have changed the database in any way so UNDO is not needed. It may be necessary to REDO the effect of the operations that are recorded in the local transaction workspace, because their effect may not yet have been written in the database.
How to backup a database?
Some of the backup techniques are as follows : 1 Full database backup – In this full database including data and database, Meta information needed to restore the whole database, including full-text catalogs are backed up in a predefined time series. 2 Differential backup – It stores only the data changes that have occurred since last full database backup. When same data has changed many times since last full database backup, a differential backup stores the most recent version of changed data. For this first, we need to restore a full database backup. 3 Transaction log backup – In this, all events that have occurred in the database, like a record of every single statement executed is backed up. It is the backup of transaction log entries and contains all transaction that had happened to the database. Through this, the database can be recovered to a specific point in time. It is even possible to perform a backup from a transaction log if the data files are destroyed and not even a single committed transaction is lost.
What is transaction log backup?
Transaction log backup – In this, all events that have occurred in the database, like a record of every single statement executed is backed up. It is the backup of transaction log entries and contains all transaction that had happened to the database. Through this, the database can be recovered to a specific point in time. It is even possible to perform a backup from a transaction log if the data files are destroyed and not even a single committed transaction is lost.
What is differential backup?
Differential backup – It stores only the data changes that have occurred since last full database backup. When same data has changed many times since last full database backup, a differential backup stores the most recent version of changed data. For this first, we need to restore a full database backup.
What happens when one instance performs recovery for another instance?
When one instance performs recovery for another failed instance, the surviving instance reads redo log entries generated by the failed instance and uses that information to ensure all committed transactions are reflected in the database. Data from committed transactions is not lost. The instance performing recovery rolls back any transactions that were active at the time of the failure and releases resources being used by those transactions.
How does Oracle Parallel Server perform instance recovery?
Oracle Parallel Server performs instance recovery by coordinating recovery operations through the SMON processes of the other running instances. If one instance fails, the SMON process of another instance notices the failure and automatically performs instance recovery for the failed instance.
What happens after Oracle instance fails?
After instance failure, Oracle uses the online redo log files to perform automatic recovery of the database. For a single instance running in exclusive mode, instance recovery occurs as soon as the instance starts up after it has failed or shut down abnormally.
What is the rollback phase of Oracle?
The rollback phase of system fault recovery in Oracle uses "non-blocking" rollback technology. This means new transactions can begin immediately after roll forward completes. When a new transaction accesses a row locked by a dead transaction, the new transaction rolls back only the changes that prevent the transaction's progress. New transactions do not have to wait for Oracle to roll back the entire dead transaction, so long-running transactions no longer affect recovery time. The Fast-start technology maximizes data availability and ensures predictable recovery time.
Why can Oracle read buffers already in the cache with the correct global lock?
Oracle can read buffers already in the cache with the correct global lock because this does not involve any I/O or lock operations.
What is an instance failure?
Instance failure occurs when a software or hardware problem prevents an instance from continuing work. The following sections describe the recovery performed after failure of instances accessing the database in shared mode.
Is instance recovery complete?
Instance recovery is complete and all data is accessible.
What files are needed to restore a database?
The files to be restored may include the control file, SPFILE, archived redo log files, and datafiles.
Why does my database shut down?
The database shuts down immediately if any of the control file copies becomes inaccessible and reports an error if you try to start it without a valid control file at each location specified in the CONTROL_FILES initialization parameter.
What does it mean when the datafile header is not null?
If ERROR is not NULL, then the datafile header cannot be read and validated. Check for a temporary hardware or operating system problem causing the error. If there is no such problem, you must restore the file or switch to a copy.
What is RMAN backup?
RMAN provides tools to let you preview which backups will be used in a restore, and to validate the contents of the backups to ensure that they can be used in future restore operations.
What does each row in a datafile mean?
Each row returned represents a datafile that either requires media recovery or has an error requiring a restore. Check the RECOVER and ERROR columns. RECOVER indicates whether a file needs media recovery, and ERROR indicates whether there was an error reading and validating the datafile header.
What happens when you lose a control file?
When one copy of the control file is lost, the database will automatically shut down. You can either copy an intact copy of the control file over the damaged or missing control file, or update the parameter file so that does not refer to the damaged or missing control file.
Can RMAN override backup?
For example, if you know a given backup is unavailable, due to a tape being stored offsite or a device being inaccessible, you can direct RMAN to not use that backup during the restore process.
How to recover from corrupted database?
Strategy to recover from database corruption —For Oracle databases, the DBA can turn on block checking using appropriate parameters to detect the presence of corrupt blocks in the database. This has a slight performance overhead, but will allow early detection of corrupt blocks caused by underlying disk, storage system or input/output (I/O) system problems. By default, RMAN also checks for corrupt blocks during backup. In later versions of Oracle, RMAN can be used to repair corrupted blocks in the database.
Why is it important to restore databases?
The ability to restore databases from valid backups is a vital part of ensuring business continuity. Backup integrity and restorations are an important piece of the IT Governance Institute’s IT Control Objectives for Sarbanes-Oxley, 2nd Edition. In many instances, IT auditors merely confirm whether backups are being performed either to disk or to tape, without considering the integrity or viability of the backup media.
Why are backups not useful?
Backups are of no use if the IT team cannot restore the data to the system at the time of need. A DBA should formulate a detailed strategy for this task:
What is the primary responsibility of the database administration team?
The primary responsibility of the database administration team is to review all types of RDBMSs in the enterprise and to develop a comprehensive backup plan to conduct effective backup management by proactively monitoring backups, getting alerted for failed backups and rerunning these seamlessly, without loss of time. It is good practice to back up data to physical disk and to then archive the data to tape for disaster recovery purposes.
What is the role of a database administrator?
One of the key responsibilities of a database administrator (DBA) is to prepare for the possibility of media, hardware and software failure as well as to recover databases during a disaster. Should any of these failures occur, the major objective is to ensure that the database is available to users within an acceptable time period, while ensuring that there is no loss of data. DBAs should evaluate their preparedness to respond effectively to such situations by answering the following questions:
How can IT auditors assist in data recovery?
IT auditors can assist data administration teams in strengthening their controls and data recovery processes by validating the DBA operations, including the testing of the recovery of data. This continuous, proactive and cooperative effort between internal audit and the DBA team can provide assurance to management that, in the event of a disaster, the business’s data can be recovered.
What is a database parameter file?
Database parameter file—A parameter file or server parameter file (SPFILE) defines persistent initialization parameters of a database, including information about database control files.
How to restore database in SQL Server?
Below are some reasons that could interfere with the restore process and throw the ‘ restore of database failed because the database is in use ’ error: 1 You are connected to the database you are trying to restore. 2 While using SQL Server Management Studio (SSMS) to do a database restore, you have more than one window open in it. 3 Other users are connected to the master db.
How to fix SQL Server restore failed?
This blog explained how to fix the SQL database restore failed, database in use problem. You can disconnect active users by closing the existing connections or by changing from multiple-user mode to single-user mode. Or, disconnect all the users by restarting the SQL Server service. But, if you still have issues restoring the db, Stellar SQL Database Toolkit can come in handy. It helps resolving the issue by repairing the corrupt SQL db or by recovering the SQL Server backup file.
What is Stellar Toolkit for SQL Server?
Stellar Toolkit for MS SQL software can also help you reset lost or forgotten SQL Server Administrator and user passwords. You can read the software review done by MVP from here.
How to close a connection to a SQL database?
Method 1 – Close the existing connections to the database. To close existing connections to SQL db, follow these steps: Step 1: Open SSMS and connect to the db. Step 2: After connecting to the database, Object Explorer panel will appear on the left side of the SSMS window . Step 3: In Object Explorer panel, right-click Databases, ...
Can you restore a database with more than one window?
While using SQL Server Management Studio (SSMS) to do a database restore, you have more than one window open in it.
Can SQL Server be restored from a bak file?
Tip: SQL Server database can be restored from the backup (.bak) file. But, the database restore operation may fail if the .bak file is corrupt. Use Stellar Toolkit for MS SQL software that comes with an efficient SQL backup extractor tool designed to help database administrators recover SQL database from corrupted backup (.BAK) file. The software supports SQL Server 2019, 2017, 2016, 2014, 2012, & older versions.
How to repair a database in Access?
Step 1: In your Access database, click ‘File’. Step 2: From the window that appears, click the ‘Compact & Repair’ option on the ‘Info’ page. Figure 1 – Compact and Repair an Access Database. Access will create a copy of the compacted and repaired database at the same location as that of the original database.
How to Repair Microsoft Access Database?
Tip! Check out this article on MDB repair for information about repairing MS Access 2003 or a lower version database.
Why is my database corrupted?
If multiple users of the same database have different Jet service packs and updates installed, minor differences in the MDB file format and file-locking mechanisms can cause database corruption.
How to fix corrupt Access database?
Tip: Troubleshooting corruption in the MS Access database manually may take significant time, increasing the risk of data loss. Use Stellar Repair for MS Access software to quickly repair corrupt Access database and recover all its objects, like tables, queries, forms, reports, and other objects. Download the free trial version of the software to validate the accuracy of recoverable data.
Why is the lock file deleted?
The file helps in keeping track of all active users accessing the database. When a user who last uses the database closes the database file, the lock file is deleted automatically. But, it might not get deleted if the user doesn’t have delete permissions to the Access database (.mdf) file or the database is corrupt.
What happens if a virus infects a file needed by the Access database?
If a virus infects a file needed by the Access database and once that file is used when the database opens, the infection will spread to the database and corrupts it.
What is corruption in Access?
Corruption in MS Access database usually occurs when errors are found in the underlying binary file format of the database. When that happens, you may face random errors or difficulty in accessing Access database files (.MDB/.ACCDB files).
Why is SQL Server database restoring?
The SQL Server database restoring issue is sometimes due to your login using the target database as its default database, which will always keep a connection session alive. To fix it, you need to change the default database back to “master”.
Why does SQL Server restore fail?
Since the SQL Server restore may fail because the database is used by other users, you can switch SQL Server to single user mode, and then set it to multi user mode again. This will close all the active connections as well.
How to restore SSMS database?
1. Similar with normal operation, launch SSMS and connect to your instance, then right-click the database you want to restore and choose Tasks > Restore > Database.
Why is my SQL database stuck in restoring?
What causes SQL database stuck in restoring issue? It could be that another user is using the database, or the database file is synchronized during the re-establishing process, or users not closing the SQLQuery window after finishing a query task. Anyway, you can try out the following proven ways to fix it.
What does "overwrite existing database" mean?
Overwrite the existing database (s): With this option ticked, the backed up databases will overwrite the existing databases of the same names. Otherwise, the databases with the same names will be skipped during restoring.
What does Execute it do before restore?
Execute it to destroy all existing connections before restore.
Can SQL Server backup be done on LAN?
As a comprehensive backup solution, it works not only for SQL Server databases, but also for computer data like files, partitions, OS and disks. With it, you can even perform centralized system backup for all computers within LAN.
