The Fifth Database

Guy Twena SQL Server Consultant

Agenda

• The master database in 2000• What is The Fifth Database• Querying metadata of the Resource Database• DAC• Memory objects tables – PSS & EX• Making changes to the resource database• Backup and restore to the resource database• Moving The Resource Database• Examples• Q&A

The master database in 2000 (BC)

• Upgrading sql server 2000 required dropping system objects and recreating them

• In sql server 2000 it was very easy to make changes to the master Database

What is the fifth database

• Mssqlsystemresource - introduced in sql 2005• Read-only, contains all the system objects.• Does not contain user data or user metadata.• Easier upgrading to a new version of SQL Server • Its easier to rollback you can just replace the

ResourceDB• The id of the resource DB is 32767• The default location of the file is in the binn directoy

“MSSQL$Instance\MSSQL\binn”• It important not to put the resource database on

compressed volume

Querying metadata of the Resource Database

DAC

• DAC – Dedicated Administrator Connection• The purpose of the DAC is to allow you to connect the

server if its not responding• Only one DAC can be connected at any time• In order to connect with DAC for server with instance,

the browser service must be running• The User must be from the sysadmin server role• You can view the content of system objects in each of

the user Databases

DAC – Dedicated Administrator Connection

• In order to connect with DAC you can use the following:– Sqlcmd –A –S<server\instance>– Sqlcmd–Sadmin:<server\instance>– Sqlcmd -S<server\instance>,<DAC Port>– Using SSMS, using “New Query” .

Note: connecting DAC with “Object Explorer” will not work!!! ; You will receive the following error:“Dedicated Administrator Connection are not supported”

• In order to open the DAC Connection to remote computers,sp_configure “remote admin connections”

Memory objects tables – PSS & EX

• PSS – Process Storage Structure, – holds information about your login details, network address, last

command that run, query and query poison etc.

• EX – Execution Context – is what is passed to the CPU queue e.g:when the process is sleeping

• PSS and EX Objects are stored in array and are constantly updates as any change

Memory objects tables – PSS & EX

The table SYSSESSIONS doesn’t exists in the mdf file, you won’t be able to find its data with hex editor

Making changes to the resource database & System Tables

• Using DAC.• single user mode (-m).• still you won’t be able to see the database in sys.databases. • “use mssqlsystemresource” will change the context to the resource

database• DBCC CHECKCATALOG

Hacking The Resource Database

Backup and restore to the resource database

• SQL Server cannot back up the Resource database.

• In order to backup the resource database you need to copy the file manually

• you cannot use SQL Server to restore the resource database backups.

• Restoring a backup copy of mssqlsystemresource.mdf can only be done manually, and you must be careful not to overwrite the current Resource database with an out-of-date or potentially insecure version

Moving The Resource Database

• SQL Server 2005 – the resource database had to be in the same folder as the masterDBin order to move the resource Database we should start the SQL Server with –f;-T3608

• SQL Server 2008 – the resource Database was located in the “/binn” folder of every instance, but we could move it

• SQL Server 2008R2 the location of the resource Database is in the /Binn folder but you cann’t move it

Examples

• Viewing the sys.databases definition• Different in objects that are in the master and the

resource DB• Changing column name• Reading the content of the resource database• Drop DB• how much does your data change?• Adding new SP to the resource Database

Example - how much does your data change?

• Affects the transaction log sizes • Affects the backups Size• The load on your server• In SQL 2000 we had sysindexes.rcmodctr that

keeps track of how many rows have changed• In SQL server 2008 we have

sys.sysrscols.Rcmodified that can be viewed with the DAC Connection

Examples

• Viewing the sys.databases definition• Different in objects that are in the master and the

resource DB• Changing column name• Reading the content of the resource database• Drop DB• how much does your data change?• Adding new SP to the resource Database

Questions?

The end