DBA Activites

DBCC Commands @ SQL Server

DBCC (Database consistency checker) act as Database console commands for SQL Server to check database consistency.

They are grouped as:

Maintenance

Miscellaneous

Validation

A brief description of the DBCC command categories is given below.

Maintenance: Maintenance tasks on a database, index, or filegroup.

Miscellaneous: Miscellaneous tasks such as enabling trace flags or removing a DLL from memory.

Informational: Tasks that gather and display various types of information.

Validation: Validation operations on a database, table, index, catalog, filegroup, or allocation of database pages.

Uses Of DBCC:

DBCC give details in form of statistics about the SQL Server. They can be used for Maintenance of database, index, or filegroup. DBCC Commands can be used to perform validation operations on a database, table, index, catalog, filegroup, or allocation of database pages.

They can perform miscellaneous tasks such as enabling trace flags or removing a DLL from memory. DBCC INDEXDEFRAG, DBCC ERRORLOG, DBCC CACHESTATS are one of the few DBCC commands

List of frequently used DBCC Command

  1. DBCC CHECKCATALOG

Used to perform consistency check for a table/catalog for a particular database.

  1. DBCC CHECKCONSTRAINTS

Used to check integrity of a particular constraint or all constraints on a particular table for a database.

  1. DBCC CHECKALLOC

Used to check page usage and allocation of a database.

  1. DBCC CHECKTABLE(tablename)

Used to verify data page integrity, page offsets, data page links, page pointers, index pointers, index sort order for a specified table.

  1. DBCC SQLPERF(logspace)

Displays T-log size and space used % for all databases.

  1. DBCC SHOWFILESTATS

Display Extent information for a database.

  1. DBCC CHECKIDENT(tablename)

Used to check identity information or to return current identity value for a particular table.

  1. DBCC TRACEOFF

Used to disable tracing

  1. DBCC TRACEON

Used to enable tracing.

  1. DBCC TRACESTATUS

Displays the trace status.

  1. DBCC USEROPTIONS

Displays the active SET options for a particular database

  1. DBCC INPUTBUFFER(sessionid)

Used to get the last statement sent by session to SQL server.

  1. DBCC SHRINKDATABASE(databasename)

Used to shrink data and log files for a particular database. It release the free space to OS.

  1. DBCC SHRINKFILE(file_id)

Used to shrink individual database files.

  1. DBCC LOGINFO

Displays virtual log file information contained in a T-log file.

  1. DBCC HELP(<dbcc command>)

Displays the syntax of a DBCC command. To know syntax of DBCC SQLPERF, execute

  1. DBCC MEMORYSTATUS

Displays SQL Server memory allocation status.

  1. DBCC Cleantable

Used to reclaim space from dropped variable length columns in tables/indexed views

  1. DBCC Opentran

Displays information about oldest active transaction and oldest distributed and non-distributed replication transaction

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