Interview Questions and Answers

IBM DB2 is a family of data management products, including database servers, developed by IBM.

A stored procedure is a set of SQL and procedural statements that are stored on the database server and can be invoked by a client application or another stored procedure.

The COMMIT statement in DB2 is used to save all the changes made during the current transaction to the database.

A foreign key is a column or set of columns in a table that refers to the primary key of another table. It establishes a link between the two tables.

A trigger is a set of SQL statements that are automatically executed, or 'triggered,' in response to a specified event on a particular table or view.

DB2 is known for its advanced features like pureXML, Time Travel Query, and deep compression, setting it apart from other relational databases.

A clustered index determines the physical order of data in a table. In DB2, it is implemented using the CLUSTERED keyword during table creation.

Both primary and unique keys enforce the uniqueness of values, but a table can have only one primary key, while it can have multiple unique keys.

A cursor is a database object that allows for both fetching and updating rows from a result set one at a time.

The RUNSTATS command is used to collect statistics about the data in tables and indexes, helping the query optimizer to generate efficient query plans.

ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties ensure the reliability of database transactions.

A buffer pool is a memory area used to cache table and index data to reduce the I/O operations and improve query performance.

The LOAD utility is used to efficiently load large amounts of data into DB2 tables. It is faster than using SQL INSERT statements for bulk data loading.

A view is a virtual table based on the result of a SELECT query, while an MQT is a physical table that stores the result of a query, and its data is updated periodically.

A DB2 package is a compiled set of SQL statements and procedures stored in the database. It can be executed by database applications.

The REORG utility is used to reorganize the physical storage of tables and indexes, optimizing space usage and improving query performance.

The RUNTIMESTATS option is used to collect runtime statistics for SQL statements, providing information about resource usage during query execution.

The db2ckpwd utility checks the strength of user passwords in DB2, helping to enforce security policies and prevent weak passwords.

A correlated subquery is a subquery that refers to columns from the outer query. It is executed once for each row processed by the outer query.

The EXPORT utility is used to export data from DB2 tables, while the IMPORT utility is used to import data into DB2 tables. They are often used for data migration and backups.

A package bind is the process of associating a package, which contains the compiled form of SQL statements, with a database. It is a crucial step in executing SQL statements.

The LOAD RESUME option allows the loading of data to resume from the point of failure in case of a previous load failure, reducing the need to reload all data.

The db2move command is used for copying or moving data between databases. It is particularly useful for exporting and importing data in a structured manner.

A table space is a container for database objects such as tables, indexes, and long field columns. It provides a logical grouping of related objects for storage management.

A correlated scalar subquery is a subquery that returns a single value and is evaluated once for each row processed by the outer query, using values from that row.

The db2pd command is used to display information about various aspects of the DB2 instance, such as memory usage, locks, and active applications.

The REBIND command is used to rebind packages in DB2, refreshing the access plan and optimizing the SQL statements after changes to the database or its statistics.

The db2exfmt command is used to format the output of the EXPLAIN statement, providing a more readable and understandable representation of the access plan.

The db2look command is used to generate SQL statements that can recreate the structure and data of a database, including tables, indexes, and constraints.

Isolation level determines the degree to which one transaction must be isolated from resource changes made by other transactions.

The EXPLAIN statement is used to analyze and optimize SQL queries by providing information about the access path chosen by the DB2 optimizer.

DB2 uses various concurrency control mechanisms, including locks and isolation levels, to ensure that transactions execute without interference from other transactions.

Performance can be improved by creating indexes, optimizing SQL queries, updating statistics, and using proper join and filter conditions.

An index is a data structure that provides a quick and efficient way to look up and access data in a table. It improves query performance by reducing the number of rows that need to be scanned.

The db2diag.log file contains diagnostic information about the database manager and its associated processes. It is used for troubleshooting and monitoring.

Locking can be monitored using tools like db2pd and improved by using proper isolation levels, avoiding long-running transactions, and optimizing SQL queries.

Data partitioning is a feature in DB2 that allows tables and indexes to be divided into smaller, more manageable pieces, improving query performance and parallelism.

The db2dart utility is used for database analysis and recovery. It can be used to check the consistency of database objects and repair certain types of corruption.

Database performance can be monitored using tools like db2top and db2mon. Performance can be managed by optimizing SQL queries, updating statistics, and configuring buffer pools.

The db2relocatedb command is used to move a database from one directory path to another. It helps in relocating databases without requiring a full backup and restore.