- Introduction
- Undocumented DBCC commands:
- DBCC BUFFER
- DBCC BYTES
- DBCC DBINFO
- DBCC DBTABLE
- DBCC DES
- DBCC HELP
- DBCC IND
- DBCC LOG
- DBCC PAGE
- DBCC PROCBUF
- DBCC PRTIPAGE
- DBCC PSS
- DBCC RESOURCE
- DBCC TAB
- Literature
Introduction
In this article I want to tell you about some useful undocumented
DBCC commands, and how you can use these commands in SQL Server 2000
for administering and monitoring.
DBCC is an abbreviation of a Database Console Command.
This is the description of DBCC from SQL Server Books Online:
The Transact-SQL programming language provides DBCC statements that
act as Database Console Commands for MicrosoftR SQL Server 2000.
These statements check the physical and logical consistency of a
database. Many DBCC statements can fix detected problems.
Undocumented DBCC commands
1. DBCC BUFFER
This command can be used to print buffer headers and pages from the
buffer cache.
Syntax:
dbcc buffer ([dbid|dbname] [,objid|objname] [,nbufs], [printopt])
where
dbid|dbname – database id|database name.
objid|objname – object id|object name
nbufs – number of buffers to examine
printopt – print option
0 – print out only the buffer header and page header
(default)
1 – print out each row separately and the offset table
2 – print out each row as a whole and the offset table
This is the example:
DBCC TRACEON (3604)
dbcc buffer(master,’sysobjects’)
2. DBCC BYTES
This command can be used to dump out bytes from a specific address.
Syntax:
dbcc bytes ( startaddress, length )
where
startaddress – starting address to dump
length – number of bytes to dump
This is the example:
DBCC TRACEON (3604)
dbcc bytes (10000000, 100)
3. DBCC DBINFO
Print DBINFO structure for specified database.
Syntax:
DBCC DBINFO [( dbname )]
where
dbname – is the database name.
This is the example:
DBCC TRACEON (3604)
DBCC DBINFO (master)
4. DBCC DBTABLE
This command prints out the contents of the DBTABLE structure.
Syntax:
DBCC DBTABLE ({dbid|dbname})
where
dbid|dbname – database name or database ID
This is the example:
DBCC TRACEON (3604)
DBCC DBTABLE (master)
The DBTABLE structure has an output parameter called dbt_open.
This parameter keeps track of how many users are in the database.
Look at here for more details:
FIX:
Database Usage Count Does Not Return to Zero
5. DBCC DES
Prints the contents of the specified DES (descriptor).
Syntax:
dbcc des [( [dbid|dbname] [,objid|objname] )]
where dbid|dbname – database id|database name.
objid|objname – object id|object name
This is the example:
DBCC TRACEON (3604)
DBCC DES
6. DBCC HELP
DBCC HELP returns syntax information for the specified DBCC statement.
In comparison with DBCC HELP command in version 6.5, it returns syntax
information only for the documented DBCC commands.
Syntax:
DBCC HELP (‘dbcc_statement’ | @dbcc_statement_var | ‘?’)
This is the example:
DBCC TRACEON (3604)
DECLARE @dbcc_stmt sysname
SELECT @dbcc_stmt = ‘CHECKTABLE’
DBCC HELP (@dbcc_stmt)
Look at here for more details:
DBCC HELP
(T-SQL)
7. DBCC IND
Shows all pages in use by indexes of the specified table.
Syntax:
dbcc ind( dbid|dbname, objid|objname, printopt = {-2|-1|0|1|2|3} )
where
dbid|dbname – database id|database name.
objid|objname – object id|object name
printopt – print option
There is change in this command in comparison with SQL Server 7.0 one:
you should specify printopt parameter (this parameter is not optional now)
This is the example:
DBCC TRACEON (3604)
DBCC IND (master, sysobjects, 0)
8. DBCC log
This command is used to view the transactional log for the specified
database.
Syntax:
DBCC log ( {dbid|dbname}, [, type={-1|0|1|2|3|4}] )
PARAMETERS:
Dbid or dbname – Enter either the dbid or the name of the database
in question.
type – is the type of output:
0 – minimum information (operation, context, transaction id)
1 – more information (plus flags, tags, row length, description)
2 – very detailed information (plus object name, index name,
page id, slot id)
3 – full information about each operation
4 – full information about each operation plus hexadecimal dump
of the current transaction log’s row.
-1 – full information about each operation plus hexadecimal dump
of the current transaction log’s row, plus Checkpoint Begin,
DB Version, Max XDESID
by default type = 0
To view the transaction log for the master database, you can run the
following command:
DBCC log (master)
9. DBCC PAGE
You can use this command to view the data page structure.
Syntax:
DBCC PAGE ({dbid|dbname}, pagenum [,print option] [,cache] [,logical])
PARAMETERS:
Dbid or dbname – Enter either the dbid or the name of the database
in question.
Pagenum – Enter the page number of the SQL Server page that is to
be examined.
Print option – (Optional) Print option can be either 0, 1, or 2.
0 – (Default) This option causes DBCC PAGE to print
out only the page header information.
1 – This option causes DBCC PAGE to print out the
page header information, each row of information
from the page, and the page’s offset table. Each
of the rows printed out will be separated from
each other.
2 – This option is the same as option 1, except it
prints the page rows as a single block of
information rather than separating the
individual rows. The offset and header will also
be displayed.
Cache – (Optional) This parameter allows either a 1 or a 0 to be
entered.
0 – This option causes DBCC PAGE to retrieve the page
number from disk rather than checking to see if it is
in cache.
1 – (Default) This option takes the page from cache if it
is in cache rather than getting it from disk only.
Logical – (Optional) This parameter is for use if the page number
that is to be retrieved is a virtual page rather then a
logical page. It can be either 0 or 1.
0 – If the page is to be a virtual page number.
1 – (Default) If the page is the logical page number.
This is the example:
DBCC TRACEON (3604)
DBCC PAGE (master, 1, 1)
Look at here for more details:
Data
page structure in MS SQL 6.5
10. DBCC procbuf
This command prints procedure buffer headers and proc-headers from
the procedure cache.
Syntax:
DBCC procbuf( [dbid|dbname], [objid|objname], [nbufs], [printopt = {0|1}] )
where
dbid|dbname – database id|database name.
objid|objname – object id|object name
nbufs – number of buffers to print
printopt – print option
(0 print out only the proc buff and proc header (default)
1 print out proc buff, proc header and contents of buffer)
This is the example:
DBCC TRACEON (3604)
DBCC procbuf(master,’sp_help’,1,0)
11. DBCC prtipage
This command prints the page number pointed to by each row on the
specified index page.
Syntax:
DBCC prtipage( dbid, objid, indexid, indexpage )
where
dbid – database ID
objid – object ID
indexid – index ID
indexpage – the logical page number of the index page to dump
This is the example:
DBCC TRACEON (3604)
DECLARE @dbid int, @objectid int
SELECT @dbid = DB_ID(‘master’)
SELECT @objectid = object_id(‘sysobjects’)
DBCC prtipage(@dbid,@objectid,1,0)
12. DBCC pss
This command shows info about processes currently connected to the
dataserver. Structure is the source of data contained in the sysprocesses
table.
Syntax:
DBCC pss( suid, spid, printopt = { 1 | 0 } )
where
suid – server user ID
spid – server process ID
printopt – print option
(0 standard output,
1 all open DES’s and current sequence tree)
This is the example:
DBCC TRACEON (3604)
dbcc pss
13. DBCC resource
This command shows dataserver level RESOURCE, PERFMON and DS_CONFIG
info. RESOURCE shows addresses of various data structures used by
the server. PERFMON structure contains master..spt_monitor
field info. DS_CONFIG structure contains master..syscurconfigs
field info.
Syntax:
DBCC resource
This is the example:
DBCC TRACEON (3604)
DBCC resource
14. DBCC TAB
You can use the following undocumented command to view the data
pages structure (in comparison with DBCC PAGE, this command will
return information about all data pages for viewed table, not
only for particular number)
Syntax:
DBCC tab (dbid, objid)
where
dbid – is the database id
objid – is the table id
This is the example:
DBCC TRACEON (3604)
DECLARE @dbid int, @objectid int
SELECT @dbid = DB_ID(‘master’)
SELECT @objectid = object_id(‘sysdatabases’)
DBCC TAB (@dbid,@objectid)
Literature
1. “What are all the dbcc commands for SQL Server?” NTFAQ
http://www.ntfaq.com/Articles/Index.cfm?ArticleID=14186
2. INFO: Description of DBCC PAGE Command
http://support.microsoft.com/support/kb/articles/Q83/0/65.ASP
3. THE UNAUTHORIZED DOCUMENTATION OF DBCC
http://user.icx.net/~huntley/dbccinfo.htm
4. The Totally Unauthorized List of Sybase DBCC Commands
http://www.kaleidatech.com/dbcc1.htm
5. The Totally Unauthorized List of Sybase DBCC Commands
http://www.kaleidatech.com/dbcc2.htm
6. The Totally Unauthorized List of Sybase DBCC Commands
http://www.kaleidatech.com/dbcc3.htm
7. FIX: Database Usage Count Does Not Return to Zero
http://support.microsoft.com/support/kb/articles/Q175/3/03.ASP
8. DBCC HELP (T-SQL)
http://msdn.microsoft.com/library/psdk/sql/dbcc_10.htm
»
See All Articles by Columnist Alexander Chigrik
