Predicting Mainframe Performance

Transcription

1 Predicting Mainframe Performance Objective This tutorial shows you how to use the calibrated model you created earlier to perform capacity planning studies and troubleshoot any performance issues. This tutorial is for users who want to perform mainframe capacity planning studies. To perform this tutorial, you need the calibrated Mainframe model from the previous Mainframe Tutorial. 1

2 Processor Utilization and ONLINE Workload First, you will see how to study the effects on the processor utilization of doubling the ONLINE workload. Using the features of the Mainframe model, you can tune the performance of your mainframe to minimize the impact of the increased workload. 1 Open the <initials>_mainframe_modeling project and switch to the mainframe_calibration scenario if you are not already in it. 2 Choose Scenarios > Duplicate Scenario 3 In the dialog box, enter the name of the scenario as Increased_Workload and click OK. You are taken to the new scenario, which has the calibrated mainframe you will use to study the increased workload. 2

3 For this purpose, we will use the Workload Scaler to increase the transactions per second (TPS) for our ONLINE Service Class. 4 From the menu, select Mainframes > Scale Transaction Rates Expand the tree on the left side to show the following screen: 5 Check the box next to Workload Config: Sample_SYS-ONLINE-ONLINE, then type the value in the textbox next to Set value for 3

4 checked items: to 100 and then click on the Scale by% button. The resulting dialog box should look like the following: 6 Click OK. 7 Choose File > Save. 8 Right-click Calibrated_Mainframe mainframe node and select Choose Individual DES Statistics. 9 Click on the box next to Mainframe and click OK. 4

5 10 Click the Configure/Run DES toolbar button, and the following Configure/Run DES dialog box appears: 11 Click Run to run the simulation 12 Click Close to close the simulation sequence window. 13 Right click on the Calibration_Model node and select View Results. 5

6 14 Click on the Processor Utilization by LPAR <Sample_SYS> to select it, and then click the Show button to open the graph for that statistic. The processor utilization is now around 60% compared to 39.5% during the calibration. There is an increase in processor utilization because of the increase in workload. Now, the goal is to reduce the effect of this increase in processor utilization by two methods: Switching from Dedicated CPs to Shared CPs Using IRD 6

7 Switching from Dedicated CPs to Shared CPs This section discusses CP types (Dedicated / Shared) and the affect these options have on how processors are allocated to LPARs. When the CP type is set to Dedicated, each of the Logical CPs assigned to an LPAR maps on to a Physical CP in the Mainframe. So, the number of Logical CPs cannot exceed the number of Physical CPs in the Mainframe. If the CP type is set to Shared, it means that the Physical CPs are shared by the LPARs, and, there is no physical limitation on the number of Logical CPs that can be allocated for each LPAR. All the Logical CPs assigned of type Shared will equally share the Physical CPs. 1 Choose Scenarios > Duplicate Scenario 2 In the dialog box, enter the name of the scenario as Shared_CP_Type and click OK. 7

8 3 Right-click on the Calibration_Model node and select Edit Attributes. 8

9 4 Edit the Mainframe Parameters > Hardware Configuration > LPAR Configuration attribute to open the LPAR Configuration table. 5 Change the CP Type for the Sample_SYS and Test_SYS LPARs to Shared. 6 Change the Number of Logical CPs for Sample_SYS to 9. 9

10 7 Click OK in all the attribute dialog boxes to return to the main project window 8 Choose File > Save. 9 Click the Configure/Run DES toolbar button, and the following Configure/Run DES dialog box appears. 10 Click Run to run the simulation. 11 Click Close to close the simulation sequence window. 12 Right click on the Calibration_Model node and select View Results. 10

11 13 Click on the Processor Utilization by LPAR <Sample_SYS> to select it, and click the Show button to open the graph for that statistic. The processor utilization is now about 40 percent compared to 60 percent, which was seen after increasing the workload. This clearly indicates that the switch from Dedicated to Shared CPs reduces the impact of the increased workload. 11

12 14 Click on the Processor Utilization by LPAR <Test_SYS> to select it, and then click the Show button to bring up the graph for that statistic. Note that this LPAR has around 45 percent utilization even though it was allocated lesser number of CPs. So, there are extra resources available to this LPAR that could be used by the Sample LPAR to meet its goals better. So, a more dynamic way is needed to manage resources amongst the LPARs. 12

13 Using IRD This section discusses the IRD (Intelligent Resource Director), and how it manages resource allocation between LPARs. IBM provides a functionality known as Intelligent Resource Director (IRD). When IRD is enabled, z/os Workload Manager and IRD dynamically allocate resources to the respective workloads in the system so that the service class goals are met. 1 Choose Scenarios > Duplicate Scenario 2 In the dialog box, enter the name of the scenario as IRD_LPARs and click OK. 3 Right-click on the Calibration_Model node and select Edit Attributes. 13

14 4 Set the Mainframe Parameters > Hardware Configuration > LPAR Resource Management to Enabled. 5 Edit the Mainframe Parameters > Hardware Configuration > LPAR Configuration attribute to open the LPAR Configuration table. 6 Change the Initial Weight for the Sample_SYS and Test_SYS LPARs to 100, and set the Number of Logical CPs for Sample_SYS to 6. IRD can only be used if the LPARs have the CP types set to shared, as the logical CP allocation for an LPAR could be changed by IRD to help the service classes in the LPAR meet their goals. 14

15 Having the weights of the LPAR in the order of hundreds allows more granular adjustment. This results in better control. The resulting dialog box looks like this. 7 Click OK in all the attribute dialog boxes to return to the main project window 8 Choose File > Save to save the project. 9 Click the Configure/Run DES toolbar button, and the following Configure/Run DES dialog box appears. 10 Click Run to run the simulation 11 Click Close to close the simulation sequence window. 15

16 12 Once the simulation completes, right-click on the Calibration_Model node and select View Results. 13 Click on the Processor Utilization by LPAR <Sample_SYS> to select it, and then click the Show button to open the graph for that statistic. The processor utilization is now less than 40 percent compared to 60 percent that we saw due to an increased workload. Initially, you may notice that the Sample LPAR utilizes 100 percent of the processor. This is because IRD allocated some 16

17 resources for the Test LPAR so that it could meet its goals. After that, IRD noticed that Sample SYS had more important workloads, and decided to change the weights to give it more resources, thus bringing down the utilization. 14 Click on the Processor Utilization by LPAR <Test_SYS> to select it, and then click the Show button to bring up the graph for that statistic. The processor utilization for the Test LPAR is not always 100%, especially at the beginning where IRD dynamically changed the weights to give more resources to the Test LPAR so that it could 17

18 meet its goals. IRD manages resources between LPARs dynamically by deciding which of them is more important and by monitoring at the workloads on each LPAR. Conclusion You used the calibrated mainframe simulation model to study the effect of increasing the workload on the mainframe, and then switched to shared CPs to reduce the impact of the increased workload. Finally, you used IRD to automatically manage resources to achieve optimum performance for your mainframe. 18