20
Sat, Apr
5 New Articles
  1. You are here:  
  2. Home
  3. IT Infrastructure
  4. System Administration
  5. TechTalk: Reduce Timeslice to Improve Performance

TechTalk: Reduce Timeslice to Improve Performance

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

For the faster AS/400 processors (B60 and above), reducing the interactive timeslice is a quick change that may improve performance on your system.

IBM recommends in the Work Management Guide that the timeslice value should be set so that about 90% of the transactions can complete within that time interval. Unfortunately, the guide does not explain why this should be so, or how to accomplish the task.

Put another way, IBM is recommending that you let 10% of your interactive transactions reach timeslice end. First, the assumption being made is that about 10% of your interactive transactions are atypical in some way. The usual culprit is batch-type work occurring in the interactive subsystem. Therefore, if on the faster AS/400s all your transactions are being completed during the default timeslice, the only way to achieve that 90% to 10% mix is to reduce the timeslice.

Since the faster AS/400 CPUs can essentially do more work in less time, the default timeslice value of 2000 for interactive work (QINTER class) could allow the atypical long-running transactions to cause the others to be unduly delayed. By reducing the timeslice, you can lessen the impact of CPU hogs, especially during peak load conditions. The reduced timeslice will allow the CPU to process more jobs in a given period of time.

During job creation on the AS/400, the job class (*CLS) object specified in the subsystem description is referenced for the timeslice value. This value defines the maximum CPU time in milliseconds that a job can have after it comes out of a long wait.

Interactive jobs routinely go to long waits when waiting for workstation input. Batch jobs typically never go to long wait. Therefore, the example given here will be reducing the timeslice of QINTER. QINTER is the name of the default interactive class and subsystem description supplied by IBM.

First, observe response times during peak load or near-peak load conditions. Second, print WRKACTJOB (Work With Active Job) reports, paying special attention to the jobs that have a plus (+) after their run priority. This indicates jobs that were not able to complete their transactions during their timeslice. OS/400 has slightly reduced their priority (by 1/128) so that other work may complete. Hence, you will see 20+ as the run priority for these jobs. Also, print WRKSYSSTS (Work With System Status) reports, paying special attention to the transition data.

These reports will serve as your benchmark. You must document the current status of your system before you attempt any changes; otherwise you will not know if your changes were successful. Additionally, you can start the performance monitor (STRPFRMON) if you are comfortable interpreting the output of that utility.

All users in QINTER must sign off. End subsystem QINTER. From the console, enter:

ENDSBS QINTER

Rename the QINTER *CLS object QINTERBK:

RNMOBJ OBJ(QINTER) TYPE(*CLS) NAME(QINTERBK)

Create a new class called QINTER to replace the original:

CRTCLS QINTER TIMESLICE(nnnnnnn) RUNPTY(20) +

TEXT('Interactive subsystem class')

where the timeslice parameter is a value from 1 to 9999999.

Start the QINTER subsystem:

STRSBS QINTER

Monitor the results.

As an example, my company's B60 currently uses a timeslice of 1200 for all interactive users.

Try reducing the timeslice 200 milliseconds at a time and observe interactive response times during peak load conditions. Monitor WRKACTJOB making sure that the 20+ jobs are not increasing. Monitor WRKSYSSTS observing that the active-wait and wait-ineligible counts do not significantly increase. Repeat the process until you arrive at an optimum timeslice value.

Steven Kontos Woodbury, New York

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$0.00 Raised:
$

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: