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IBM i Power System Upgrade: Is it needed?
Is it time to upgrade your IBM i Power System? Or do you need to upgrade your IBM i Power System? Most companies upgrade their IBM Power systems on a scheduled interval, but there are instances when response times and throughput bottlenecks cause unacceptable performance levels, and a quick fix is needed. IBM i response times and throughput rely on common system resources and can have a similar effect on performance from an end user experience, but the variables that cause them are very different and are often difficult to figure out.
IBM Power system processors, memory, SSD, disk drives and other components use a very complex set of instructions to share and distribute system resources for all the transactions on the system. When individual transactions are delayed by another transaction already using the system’s resources, they are put into a wait queue. As the IBM i workload increases, throughput increases, but so does the queuing and response times. These IBM i performance metrics can have the opposite effect on the performance experienced by the end user. In fact, high throughput can cause slower IBM i response times. Understanding the source of the bottleneck can save your company from investing in an unnecessary major upgrade.
Some performance problems can be fixed by fine tuning the IBM Power configuration. However most significant performance issues today are often due to poorly written applications accessing the IBM i DB2 database using Java and ODBC connections. IBM has well documented best practices to help developers write their code to perform optimally on the IBM i, but mistakes are sometimes made. Some third party software vendors do not always respond well to these accusations, and most will not act fast enough to alleviate your immediate problems. You can easily identify some likely application performance issues at the system level, by looking for high rates of database full opens, which is a good indicator of a performance bottleneck. Database file full opens are likely from SQL procedures or programs using native I/O. Do a PEX trace using the *DBOPEN OS event and analyze using iDoctor analyzer.
Common DB2 and SQL Performance Issues Related to I/O Operations and Disk Drives
System configuration changes that reduce CPU usage can also reduce the number of I/O operations, and will significantly improve database and SQL response times. However here are some poorly configured disk subsystem configuration changes that will hurt performance:
- Mixing disk drive sizes in the same ASP
- Subsystem has some IOAs with more disk drives than other IOAs
- Subsystem has too many disk units on the same IOA
- Subsystem has a single parity set when utilizing dual/paired SAS disk IOAs
- Use same size drives when adding new drives to an array, and stop/restart protection so all drives contain parity data to prevent increased IO request hot spots
- Adding new or additional disk drives to an ASP without using the “Add and Balance” option
- Reducing the number of disk drive arms when upgrading or migrating to a new Power system
If you are unable to modify your applications, and your best efforts have fallen short of achieving your response time or throughput objectives, talk to one of our IBM Power System experts to discuss an economical upgrade solution. Upgrading IBM Power system processing power, memory, disk drives or add SSD is not a complicated or costly investment. Adding more system resources to your IBM Power system may be a band aide in some cases, but a simple upgrade can be a quick fix to a very big problem.
For more information and help about managing your IBM i Power System peformance, read IBM's documentation here: https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_73/rzahx/rzahxmngparent.htm
