DBA Interview Questions and Answers for a DB2 on Linux, Unix and Windows DBA focusing on Server Operations.
Describe the DB2 Database Configuration Parameter – SORTHEAP?
Defines the maximum number of memory pages used for private sorts or the maximum number of shared memory pages to be used for shared ports.
In a private sort, the agent private memory is affected. If it’s a shared sort then the database shared memory is influenced.
An example of using SORTHEAP, is if an application creates regular large sorts.
Can memory information be obtained by the GET DB CFG FOR mydb SHOW DETAIL command?
Yes. View and Configure information for:
a) Self Tuning Memory (SELF_TUNING_MEM) – Indicates whether the memory tuner is ON or OFF.
b) Size of database shared memory (DATABASE_MEMORY) – Details the shared memory amount reserved for the database shared memory region.
c) Database Memory Threshold (DB_MEM_THRESH) - Defines how the database manager manages excess unused database shared memory.
What authority should a user have to QUIESCE a DB2 database?
A login account must have either SYSADM or DB2ADM to QUIESCE a database. When the database is in a QUIESCE state – the users with at least one of these criteria can access the database: SYSADM, SYSCTRL, SYSMAINT, DBADMN. The QUIESCE command allows administrative tasks to complete. When the administrative tasks are complete use UNQUIESCE to active the database.
To perform an operation against a different instance – which variable value do you change?
The environment variable “set DB2INSTANCE = [target_instance_name]” allows you to perform a task on another Instance. The alternative is to ATTACH to another instance.
The DBINSTANCE variable can also be set at the session level.
Which DB2 configuration is used to set the maximum number of applications that can execute concurrently?
MAXCAGENTS. The parameter assists in managing the load on the system during high concurrent application requests. The parameter is useful in managing in a shared environment with limited memory and high levels of connections.
To force an application to wait indefinitely to obtain a table lock, which database configuration parameter is used?
LOCKTIMEOUT. Assign a value to LOCKTIMEOUT, to detail the number of seconds an application will wait to obtain a lock.
To set LOCKTIMEOUT for an indefinite wait use “-1” . The application will wait until a lock is granted or a deadlock is present.
In contrast, assigning “0”, an application will not wait for locks.
What command disables roll-forward recovery?
The LOGARCMETH1 is the Primary Log Archive method configuration parameter.
Assigning the OFF value indicates the log archiving method is not to be used. An example of assigning the OFF value is:
UPDATE DB CFG FOR MYDB USING LOGARCMETH1 OFF;
To allow the DB2 Discovery utility to see a database , what changes must be made?
DAS server must be running and the DISCOVER configuration for DAS must be set to KNOWN or SEARCH.
When the DAS server is created the “discover” setting defaults to “search”.
Where are changes made by Self-Tuning memory recorded?
Memory tuning log files. By default they are stored in the stmmlog subdirectory.
The log files display a summary of the resource demands for each memory consumer for each tuning interval.
Which command starts an instance?
The current DB2 Database Manager instance background processes can be started by:
1) db2start or 2) START DATABASE MANAGER.
To access a database, first start DB2 at the server level then connect to the database.
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