Device Statistics and Details

Interpret the Devices screen for SAP ASE.

To monitor devices, from the Perspective Resources view, select the server to monitor, click the drop-down arrow, and select Monitor.

Note: For SAP ASE Cluster configurations, the Devices table is called Global Devices when you select the Global tab, and Private Database Device when you select the Local tab. Information in the Private Database Device table is grouped by cluster instance.

The Devices table displays information about all devices that store databases server. A device can be an entire disk drive, or any part of a disk or file system. The charts are populated by data from collection_ase_all_client_kpis, covering the current trend period.

The Devices table includes device semaphore statistics. The device semaphore controls access to device I/O; a high ratio of Device Semaphore Waits to Device Semaphore Requests indicates contention. If IO Wait Time is high enough to cause concern, you can redistribute the data on the physical devices.

The tabs at the bottom of the screen show information about the selected devices.

Tabs on the Devices Screen
  • A pie chart showing space usage on the selected device. Includes used and unused space, in megabytes, and as percentages of all the available space on the device. The title above the chart indicates the total available space.
  • Device IO/Sec – a line graph showing the rate of I/O per second on the selected device over the current trend period. The graph shows the sum of reads, writes, and asynchronous prefetch (APF) reads. Because the graph shows a rate, and the read, write, and APF read figures in the table are changes since the last refresh, the values do not correspond.
    Note: SAP Control Center does not display the Device IO/Sec graph for in-memory devices.
  • Device IO Response Time – a line graph showing the response time, in milliseconds, for I/O operations performed on the selected device.
  • Device APF Reads/Sec – a line graph showing the rate of asynchronous prefetch read operations, per second, on the selected device. APF reads indicate that table scans are taking place.
    Note: SAP Control Center does not display the Advanced tab for in-memory devices.
IO Distribution (Global Devices on shared-disk clusters only) – Details for master device I/O activities for each instance include I/O wait time, response time, APF reads and request and wait times for device semaphores.
Related tasks
Determining Device I/O Response and I/O per Second
Modifying Device Sizes
Setting Up Statistics Collection
Related reference
Engine Statistics and Details
Process Statistics and Details