Page History
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- About the Tier entity
- About the Instance entity
- About the Engine entity
- About the Device entity
- About the Data Cache entity
- About the Performance Counter or Counter Instance entity
- About the Wait Events entity
- About the Replication Server entity
- About the Replicate(d) Databases entity
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The Device entity displays predefined graphs that report on device activity and performance. The following views are available:
- Overview
- Semaphores
About getting an overview on a Device activity
The Overview displays an overtime graph, which represents Page Requests (read and write) of the device. The following information is displayed:
- Page
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- Requests. Displays the number of pages read synchronous or asynchronous and the number of pages that are written.
About viewing Semaphores
The Semaphores view displays an overtime graph, which represents Semaphore Hits and Misses. The following information is displayed:Semaphores Displays
- Semaphores. Displays the number of times that a request for a device semaphore was granted immediately and the number of times the semaphore was busy and the task had to wait for the semaphore to be released.
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The Data Cache entity displays predefined graphs that report on the activity of the Data Cache. The following views are available:
- Overview
- Cache details
About getting an overview on Data Cache activity
The Overview displays statistics that report on the Data Cache Hit Ratio and Utilization. The following information is displayed:
- Hit
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- Ratio. Displays the percentage of time a requested page was found in a cache and was found in the wash area.
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- Utilization. Displays the percentage of searches using this cache, as a percentage of searches across all caches.
About viewing Cache Details
The Cache Details view displays statistics that report on the Data Cache Buffer Wash (Pages) and large I/Os. The following information is displayed:
- Buffer Wash (Pages)
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- . Displays the number of buffers that were clean when they passed the wash marker, the number of times that I/O was already active on a buffer when entered the wash area, and the number of times that a buffer entered the wash area dirty and was not already in I/O.
- Large I/
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- O. Displays the number of times a large I/O was requested for a buffer and the number of times it was denied.
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The Performance counter or Counter Instance entity displays statistical information on the selected counter. Precise for Sybase collects counters reported by Sybase. These counters determine which aspects of the objects to monitor. For example, the Sybase Memory Object contains the Mempages_alloced counter.
The Overview displays general details of the selected counter and overtime graph, which represent the counter value. In some of the selected counters, two overtime graphs are displayed: a graph that displays the number of transactions over time and another graph that displays the counter value per committed transaction.
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Available for Sybase versions 12.5.0.3 and higher, the Wait Events entity displays the name of the wait event group, the number of waits experienced by this event group and the summed amount of time accumulated by wait events and summed occurrences.
The following view is displayed:
- Overview
About getting an overview of Wait Events
The Overview displays general details of the selected counter. The following information is available:
- Event
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- group. Displays the name of the wait type.
- Event
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- name. Provides a description of what is causing the event.
- Time waited (avg)
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- . Average time waited for wait events, over the selected time period.
- Times waited
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- graph. Displays the time waited for wait events vs. the time waited for group events.
- Wait
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- graphs. Displays the number of wait events vs. the number of wait events for group events.
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The Replication Server entity displays predefined graphs which represent statistics related to the outbound processing phase and inbound (repagent statistics) processing phase for the selected Replication Server in the Selected time frame.
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See About the Instance entity on page 85.
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The Replicate(d) databases entity displays predefined graphs which represent statistics related to the outbound processing phase and inbound (repagent statistics) processing phase for the selected database in the Selected time frame.
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You can identify a performance problem by doing one or more of the following:
- Examining the kernel utilization of Sybase over time
- Examining I/O statistics
- Examining network activity
- Examining memory bottlenecks
- Examining a specific counter over time
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You can examine a Sybase instance over time to confirm that the amount of Sybase engines configured in your system is optimal.
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Increasing the amount of time that Adaptive Server engines wait between checks may result in better throughput, because Adaptive Server engines can spend more time processing if they spend less time checking for I/O.
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To examine I/O statistics
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You can also use this information to check I/O distribution patterns over the disks and to make object placement decisions that can help balance Disk I/O across devices. For example, does the data show that some disks are more heavily used than others? If you see that a large percentage of all I/O went to a specifically named device, you can investigate the tables residing on the device and then determine how to remedy the problem.
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You can examine network traffic over a specified time period to detect bottlenecks. Network performance can be improved by one or more of the following:
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- Switch to the Network view.
- Check the ratio between the Packets graph and the Bytes graph to see if the network packet size is used to its maximum capacity.
- Consider configuring its size.
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Lack of memory or a high memory consumption rate can cause paging. A page fault occurs when a process requires code or data that is not in its working set (its space in physical memory), thereby causing the page to be retrieved from disk and written to the physical memory. If there is not enough space in the physical memory, a chosen page needs to be written to disk to free space.
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- Examine the Memory view that reports the number of pages allocated and deallocated in each time slice.
- If you spot a high value in one of the time slices, open the Activity tab to continue your analysis of the application's performance.
- Switch to the Memory view to see information about the success and failure of Memory Requests for Worker Processed in the Memory Requests graph.
- If some of the requests have failed you may need to increase the value of the
Memory per Worker Processparameter. - Switch to Data Cache view to see information on how effective cache design is. A high Hit Ratio from the Hit Ratio graph and small amount of Page Request Misses from the Utilization graph may indicate effective cache design.
- If you see a low Hit Ratio and a lot of Page Request Misses, investigate statistics for each of the Data Caches by selecting the Data Cache entity in the Association area.
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A wide range of performance counters generated by Sybase are collected by the Precise for Sybase collect instance statistics process. These performance counters are sampled every 15 minutes and displayed in this tab over time.
A performance group is a Sybase Performance Group resource, such as a Sybase Lock. Each performance group contains a few counters that determine which performance aspects to monitor. For example, the Sybase Memory Performance group contains counters called Pages Allocated (Sybase counter: mempages_alloced) and Pages Released (Sybase counter: mempages_freed).
Some performance counters have separate instances. An instance refers to a particular occurrence of a counter. For example, the Device-Counters Performance group has counters such as Disk Cache Misses (Sybase counter: p_misses) and Disk Cache Hits (Sybase counter: p_hits), but because several devices exist, each counter is divided into instances.
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