Skip to main content

Indexes on DB2

 Concept of Indexes:

An index in DB2 is a separate structure that contains a copy of selected columns or fields from a table, along with a reference to the location of the corresponding rows in the table.

Indexes are organized in a specific data structure (such as a B-tree or hash table) that allows for quick lookup and retrieval of data based on the indexed columns.

Each index entry typically consists of the indexed column values and a pointer to the actual data location.

Purpose and Benefits of Indexes:

Improved Data Retrieval Performance: Indexes allow for faster data retrieval by providing a direct path to the desired rows, reducing the need for full table scans.

Efficient Query Execution: Indexes enable the query optimizer to choose efficient access paths, such as index scans or index-based joins, leading to faster query execution times.

Reduced Disk I/O: By narrowing down the search space, indexes can minimize the number of disk blocks read during data retrieval, resulting in lower I/O overhead.

Support for Constraints and Uniqueness: Indexes can enforce uniqueness constraints by ensuring that indexed columns contain unique values or combinations, promoting data integrity.

Ordering and Sorting: Indexes can be created on specific columns to enforce a particular sort order, facilitating faster sorting and ordered result retrieval.

Types of Indexes in DB2:

B-tree Indexes: The most common type, which organizes index entries in a balanced tree structure for efficient range-based searches and equality lookups.

Bitmap Indexes: Used for columns with a limited number of distinct values, where each bit in the index corresponds to a possible column value.

Hash Indexes: Suitable for equality searches, where the index key is hashed to provide direct access to the corresponding data location.

Function-based Indexes: Created based on a function or expression applied to one or more columns, allowing for specialized search capabilities.

CREATE INDEX index_name ON table_name (column1, column2, ...)

In the above syntax:

index_name is the name you assign to the index.

table_name is the name of the table on which the index is being created.

(column1, column2, ...) specifies the column(s) included in the index.

Now let's discuss the different methods of index creation in DB2, considerations to be checked, and tradeoffs involved:

Traditional Index Creation:

This method creates an index on an existing table in a single operation.

Syntax: CREATE INDEX index_name ON table_name (column1, column2, ...)

Online Index Creation:

This method allows the creation of an index while the table remains available for read and write operations.

Syntax: CREATE INDEX index_name ON table_name (column1, column2, ...)ONLINE

Considerations before creating indexes:

Selectivity: Choose columns with high selectivity (few distinct values) and frequently used in search conditions.

Query Analysis: Analyze query patterns to identify frequently executed queries that could benefit from indexes.

Performance Testing: Perform benchmark tests to assess the impact of index creation on query performance.

Disk Space: Consider the additional disk space required to store the index structure and index entries.

Tradeoffs of index creation:

Increased Disk Space: Indexes require additional disk space, so carefully manage storage requirements.

Index Maintenance Overhead: Indexes need to be maintained and updated, which can impact insert/update/delete operations on the table.

Storage Overhead: Indexes consume storage, so consider the impact on backup and restore operations.

Query Performance: While indexes improve query performance, they may introduce overhead during data modification operations due to index updates


To mitigate the tradeoffs and ensure optimal index usage:

Regularly monitor and analyze index usage, removing or modifying indexes that are not being used effectively.

Update statistics to ensure the query optimizer has accurate information for optimal index selection.

Regularly maintain indexes, such as rebuilding or reorganizing fragmented indexes.It's important to note that the choice of index creation method, the selection of columns, and the overall index design depend on your specific database and workload characteristics. 

It's recommended to perform thorough testing and analysis, considering the specific requirements and performance goals of your DB2 environment, to make informed decisions regarding index creation and maintenance

Here are some risks and considerations to keep in mind:

Impact on Database Performance:

Creating indexes involves additional disk I/O and index maintenance operations, which can temporarily impact the performance of the database.The duration of the index creation process depends on factors such as the size of the table and the number of rows. It can range from a few seconds to several hours for larger tables.

During the index creation process, there may be increased resource utilization, including CPU, memory, and disk usage, which can affect the overall database performance and response times.

Locking and Blocking:

Depending on the DB2 isolation level and locking configuration, creating an index on a table might require locks on the table, potentially causing blocking or contention with concurrent transactions.

Locking conflicts can impact the availability of the database and might result in transaction delays or timeouts.

Downtime or Maintenance Window:

In some cases, creating indexes on large tables or in heavily loaded production environments might require a maintenance window or a scheduled downtime to minimize the impact on ongoing operations.

It is recommended to perform index creation during periods of low database activity to minimize disruptions.

Backup and Recovery Considerations:

Before making any changes to the production database, it is crucial to ensure that proper backups and recovery mechanisms are in place.

In the unlikely event of issues or unexpected behavior during index creation, having recent backup allows you to restore the database to a known good state.

To mitigate the risks associated with creating indexes on a live production database:

Thoroughly test the index creation process in a non-production environment that closely resembles the production environment to understand the potential impact and performance implications.

Analyze the workload patterns and query requirements to identify the most beneficial indexes and prioritize their creation accordingly.

Consider scheduling the index creation during off-peak hours or low activity periods to minimize disruption to the production system.

Communicate the planned index creation activity to stakeholders and users to manage expectations regarding potential temporary performance degradation.


You might find these interesting

How to properly Start/Stop SAP system through command line ?

Starting/stopping an SAP system is not a critical task, but the method that most of us follow to achieve this is sometimes wrong. A common mistake that most of the SAP admins do is, making use of the 'startsap' and 'stopsap' commands for starting/stopping the system.  These commands got deprecated in 2015 because the scripts were not being maintained anymore and SAP recommends not to use them as many people have faced errors while executing those scripts. For more info and the bugs in scripts, you can check the sap note 809477.  These scripts are not available in kernel version 7.73 and later. So if these are not the correct commands, then how to start/stop the sap system?  In this post, we will see how to do it in the correct way. SAP SYSTEM VS INSTANCE In SAP, an instance is a group of resources such as memory, work processes and so on, usually in support of a single application server or database server with

sapstartsrv is not started or sapcontrol is not working

 What is sapstartsrv ? The SAP start service runs on every computer where an instance of an SAP system is started. It is implemented as a service on Windows, and as a daemon on UNIX. The process is called  sapstartsrv.exe   on Windows, and   sapstartsrv   on UNIX platforms. The SAP start service provides the following functions for monitoring SAP systems, instances, and processes. Starting and stopping Monitoring the runtime state Reading logs, traces, and configuration files Technical information, such as network ports, active sessions, thread lists, etc. These services are provided on SAPControl SOAP Web Service, and used by SAP monitoring tools (SAP Management Console,  SAP NetWeaver  Administrator, etc.). For more understanding use this link : How to check if it is working or not ? In case of linux , you can simply ps -ef | grep sapstartsrv In case of windows, you need

ST03N : The chapter for all BASIS Admins

This blog is targeted to BASIS ADMINS Transaction for workload analysis statistical data changed over time are monitored using transaction code ST03 , now ST03N (from SAP R/3 4.6C) . With SAP Web AS 6.4 the transaction ST03 is available again. From time to time ST03 and ST03N has seen many changes but later in SAP NW7.0 ST03N has reworked in detail specially processing time is now shown in separate column. Main Use of ST03N  is to get detailed information on performance of any ABAP based SAP system. Workload monitor analyzes the statistical data originally collected by kernel. You can compare or analyze the performance of a single application server or multiple application server. Using this you start checking from the entire system and finding your way to that one application server and narrowing down to exact issue. By Default :- You see data of current day as default view , you can change the default view. Source of the image : Let's discuss the WORKLOAD MONITOR By D

HANA System Replication - Prerequisites & Setup

Hey Folks! Welcome back to Hana high availability blog series. In our last blog we checked out operation & replication modes in hana system replication. If you haven't gone though that blog, you can checkout  this link In this blog we will be talking about the prerequisites of hana replication and it's setup. So let's get started. When we plan to setup hana system replication, we need to make sure that all prerequisite steps have been followed. Let's have a look at these prerequisites. HANA System Replication Prerequisites: Primary & secondary systems should be up & running HDB version of secondary should be greater than or equal to Primary database sever But, for Active/Active(read enabled config), HDB version should be same on both sites. System configuration/ini files should be identical on both sides Replication happe

Emergency Analysis and Troubleshooting for HANA

Why can SAP HANA go offline ?      Power failure in data center causes downtime.      Server-level hardware failures (CPU/memory) contribute.      Storage-level hardware failures (disk) impact operations.      Network-level hardware failures (switches/router) disrupt connectivity.      Operating system errors (Linux) lead to downtime.      Storage system errors (SAN/NAS) contribute to issues.      Database errors (SAP HANA) affect overall performance.      Human errors in server, router, storage, Linux, and SAP HANA cause downtime. What is the system down scenario? In this situation Hana cannot be accessed through sql or any other connection method. SAP Hana cockpit might only be partially connect to the SAP HANA system Network Check: Ping selected hosts in the data center. Ensure stable and responsive network connections. Because external and internal network connections are important for a SAP HANA system. You should test both by pinging SAP HANA and non-SAP HANA hosts in your networ

How to resolve Common Error : Standard Template "sap_sm.xls" missing

Hey everyone, putting forward a common error we usually face when we have “ Excel inplace” functionality enabled in our SAP system. This error occurs when validity of the signature of SAP standard templates expired or were incorrectly delivered via support packages. We can reproduce the error by doing as below.. Click on “spreadsheet” icon after any SAP ALV grid view of data is on screen to make this data to export into excel directly from SAP.

HANA hdbuserstore

The hdbuserstore (hana secure user store) is a tool which comes as an executable with the SAP Hana Client package. This secure user store allows you to store SAP HANA connection information, including user passwords, securely on clients. With the help of secure store, the client applications can connect to SAP HANA without the user having to enter host name or logon credentials. You can also use the secure store to configure failover support for application servers in a 3-tier scenario (for example, SAP Business Warehouse) by storing a list of all the hosts that the application server can connect to. To access the system using secure store, there are two connect options: (1)key and (2)virtualHostName. key is the hdbuserstore key that you use to connect to SAP HANA, while virtualHostName specifies the virtual host name. This option allows you to change where the hdbuserstore searches for the data and key files. Note

SAP system migration blog series - part 1: migration overview

Summary : This blog is part 1 of the blog series on SAP system migration. In this blog, we will provide overview about SAP migration, types of migration, their differences and usage scenario. SAP migration overview :   As the Greek philosopher, Heraclitus, said: “change is the only constant.” Same goes within SAP world too, often customer have to change the SAP systems along with its underlying components to meet the changing requirements, be it change from old hardware to new one, changing operating system, database. This change in SAP system components (DB, OS or Hardware) is termed as migration. Before we go into details of migration, let’s understand architecture of a typical SAP system.   An SAP system consist of SAP application instances, running on database (DB), hosted on operating system (OS), provisioned on hardware. Change in any one or more of these underlying components (DB, OS or hardware) warrant us to perform migration. Types of migration:   Broadly, there are two types

Complete Guide : XPI Inspector Tool

Content of this blog :           What is an XPI Inspector Tool ? Why XPI Tool is used ? XPI standard URL How to check XPI Tool version ? How to Install/Update XPI version using TELNET How to Use XPI Tool ? References – SAP Notes What is XPI Inspector tool ?          -    XPI Inspector is a diagnostics web application developed by SAP that collects logs and debug traces from various PI components in a very simple way and is useful for SAP PI consultants, developers, and administrators to get more insights on an issue. Why XPI is used  – 1.  Used to collect traces and logs from Messaging system or XI module. 2. Used to collect the related information to solving the issues or improving the PI or PO systems’ performance. 3. Using XPI Inspector application you will be able to collect a lot of information about your system that will help you to learn about problems in the past, to analyze new and detect such at an early stage. 4. Performs certain number of configuration checks, such as SSL c

Work Process and Memory Management in SAP

Let’s talk about the entire concepts that are related to memory when we talk about SAP Application. Starting with few basic terminologies, Local Memory :  Local process memory, the operating system keeps the two allocation steps transparent. The operating system does the other tasks, such as reserving physical memory, loading and unloading virtual memory into and out of the main memory. Shared Memory :  If several processes are to access the same memory area, the two allocation steps are not transparent. One object is created that represents the physical memory and can be used by various processes. The processes can map the object fully or partially into the address space. The way this is done varies from platform to platform. Memory mapped files, unnamed mapped files, and shared memory are used.  Extended Memory : SAP extended memory is the core of the SAP memory management system. Each SAP work process has a part reserved in its virtual address space for extended memory. You can set