26
Thu, Dec
0 New Articles
  1. You are here:  
  2. Home
  3. Analytics & Cognitive
  4. DB2
  5. TechTip: Fine-Tuning Db2 Symmetric Multiprocessing (SMP) to Improve Performance for Long-Running Queries

TechTip: Fine-Tuning Db2 Symmetric Multiprocessing (SMP) to Improve Performance for Long-Running Queries

Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

SMP causes long-running queries to complete faster but consume more resources. Therefore, SMP shouldn’t be used in all situations; consider carefully how SMP is applied in your environment.

By default, when a query is run, only a single process is used to run the query. Db2 Symmetric Multiprocessing (SMP) allows queries to use multiple, parallel processes when running a query in order to complete faster. This is achieved by allowing the database to use multiple CPUs and I/O processors to work on the query at the same time. SQL queries, OPNQRYF, Query/400, index creation and maintenance, and reorganizing of physical files can all take advantage of SMP. This powerful tool can result in these operations running more quickly but will cause increased consumption of main storage, CPU, and disk resources. Therefore, SMP isn’t always the best choice, and it’s important to choose wisely how and when to use SMP.

Long-running queries benefit the most from SMP. For a long-running query, such as one that utilizes OLAP functions, the additional overhead of running multiple, parallel tasks is small in comparison to the length of time it takes to run the query. However, in short-running queries, SMP may actually cause your query to perform worse because of the additional overhead. Therefore, new and enhanced controls were introduced in IBM i 7.5 to allow you to better control how SMP is used in your environment. These controls are set using the QAQQINI options file. These new and enhanced options are:

  • PARALLEL_DEGREE: Control the maximum number of tasks allowed per query
  • PARALLEL_MAX_SYSTEM_CPU: Dynamically adjust running queries to keep CPU usage below a safe threshold
  • PARALLEL_MIN_TIME: Set the minimum time a query must run before it can use parallel processing

PARALLEL_DEGREE *OPTIMIZE

This QAQQINI option is used to control how much processing power the optimizer can consider for use during optimization. By default, the optimizer assumes it can use as many tasks as there are cores on the system. The PARALLEL_DEGREE option allows you to set the number of tasks allowed to either *NONE, *MAX, *NBRTASKS, or *OPTIMIZE. The *OPTIMIZE option allows the query optimizer to choose the best implementation and is the recommended option because it allows the optimizer the greatest flexibility in how a query is run.

In IBM i 7.5, the *OPTIMIZE [percentage] option was enhanced. The default value is 100%; however, you can change this default by setting the percentage to a number between 1 and 200. By setting the percentage to less than 100, you reduce the number of tasks the optimizer considers available for use. Previously, this setting only applied after the optimization finished but before the query executed. Now the SQL Query Engine (SQE) will apply the percentage during optimization, allowing the optimizer to make a better, more accurate decision on the number of tasks the query will run with.

PARALLEL_DEGREE can be set using the QAQQINI options file, the CHGQRYA CL command, or the system value QQRYDEGREE.

PARALLEL_MAX_SYSTEM_CPU

This QAQQINI option protects your system from being overloaded by dynamically adjusting queries to keep the CPU usage below a safe threshold. By default, when the CPU usage exceeds 80%, SMP enabled queries will experience a gradual reduction in the number of tasks used until the CPU usage falls back below 80%. There will always be at least one task running to process the query, which allows the queries to slow down but not stop processing. Once the CPU usage drops below 80%, any tasks that were suspended will be reinstated if there are additional resources available. In IBM i 7.5, the default value of 80% can now be modified using the QAQQINI option PARALLEL_MAX_SYSEM_CPU. This option is available only in IBM i 7.5 and is valid only when PARALLEL_DEGREE is set to *OPTIMIZE.

PARALLEL_MIN_TIME

This QAQQINI option allows you to set the minimum time a query must run before it uses parallel processing. This allows you to only use SMP for the long-running queries that can benefit from using multiple parallel tasks. The optimizer starts out processing a query using only one task. If a query has not yet returned any data, and it runs longer than the time configured, then the query will be re-optimized to use SMP and the new plan swapped in. If a query has returned data, the query will run to completion and will be re-optimized with SMP the next time it is run. The default time before considering using SMP is 60 seconds. This default can now be modified to a different minimum time using the QAQQINI option PARALLEL_MIN_TIME. This option is available only in IBM i 7.5 and is valid only when PARALLEL_DEGREE is set to *OPTIMIZE.

No-Charge Option

In 2022, Db2 Symmetric Multiprocessing (SMP) switched to a no-charge option. Db2 Symmetric Multiprocessing is 5770SS1 option 26, and it must be ordered and installed separately. You can check to see if it is installed with the following query:

SELECT SYMBOLIC_LOAD_STATE 
    FROM QSYS2.SOFTWARE_PRODUCT_INFO 
    WHERE PRODUCT_ID = '5770SS1' 
      AND PRODUCT_OPTION = '26'

Find Out More

To learn how to set up and use the QAQQINI query options file, see https://www.ibm.com/docs/en/i/7.5?topic=attributes-qaqqini.

For more information about these improvements to SMP processing, see https://www.ibm.com/support/pages/node/6579159.

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: