17.05 - Process Scheduling: Cylinder Read Columns - Teradata Database

Teradata Vantageā„¢ - Resource Usage Macros and Tables

prodname
Advanced SQL Engine
Teradata Database
vrm_release
17.00
17.05
created_date
June 2020
category
Administration
User Guide
featnum
B035-1099-170K

These columns represent the File System resource usage statistics. The Cylinder Read feature uses these statistics for tracking performance and utilization.

Column Name Mode Description Data Type
FileFcrRequests count Total number of requests for the File System to use Cylinder Read.

This column records the number of attempts to use Cylinder Read independent of whether the request will be issued to FSG or not. A request can be denied due to insufficient data blocks or because there is insufficient space in the FSG cache. Requests can also be denied at both the user and kernel level. Each of these items is counted in other FileFcr resource usage columns.

This column can perform a number of calculations:

  • Requests issued to FSG =

    FileFcrRequests - FileFcrDeniedUser

  • Successful Cylinder Reads =

    FileFcrRequests - FileFcrDeniedUser - FileFcrDeniedKern

FLOAT
FileFcrRequestsAdaptive count Number of adaptive requests from File System.

This column records the number of requests for adaptive-style Cylinder Reads.

This column is not currently used.
FLOAT
FileFcrBlocksDeniedCache count Number of data blocks contained in Cylinder Read requests rejected by the FSG subsystem due to insufficient cache.

This column records the number of data blocks that were part of attempts to use Cylinder read that were denied by the FSG subsystem due to insufficient cache space; therefore, also incremented the FileFcrDeniedCache column.

FLOAT
FileFcrBlocksDeniedKern count Number of data blocks contained in the FSG subsystem rejected requests for Cylinder Read.

This column records the number of data blocks that were part of attempts to use Cylinder Read that were denied by the FSG subsystem, and therefore, also incremented the FileFcrDeniedKern column.

FLOAT
FileFcrBlocksDeniedUser count Number of data blocks contained in the File System rejected requests for Cylinder Read.

This column records the number of data blocks that were part of attempts to use Cylinder Read that were denied by the File System.

FLOAT
FileFcrBlocksDeniedThreshKern count Number of data blocks contained in Cylinder Read requests rejected for threshold by the FSG subsystem.

This column records the number of data blocks that were part of attempts to use Cylinder read that were denied by the FSG subsystem due to the number of blocks being below the threshold, and therefore, also incremented the FileFcrDeniedThreshKern column.

FLOAT
FileFcrBlocksDeniedThreshUser count Number of data blocks contained in Cylinder Read requests rejected for threshold by the File System.

This column records the number of data blocks that were part of attempts to use Cylinder Read that were denied by the File System due to the number of blocks being below the threshold, and therefore, also incremented the FileFcrDeniedThreshUser column.

FLOAT
FileFcrBlocksRead count Number of data blocks read in using Cylinder Read.

This column records the total number of data blocks read in by successful Cylinder Read operations.

The average number of data blocks in a successful Cylinder read can be calculated as follows:

Average data blocks/ Cylinder Read = FileFcrBlocksRead / (FileFcrRequests - FileFcrDeniedUser - FileFcrDeniedKern)

FLOAT
FileFcrDeniedCache count Number of Cylinder Read requests denied by FSG due to insufficient cache.

This column records the number of Cylinder Read requests denied due to insufficient FSG cache space for a cylinders worth of data.

FLOAT
FileFcrDeniedKern count Number of Cylinder Read requests denied by the FSG subsystem.

This column records the number of Cylinder Read requests issued to the FSG subsystem which, for any reason, have been denied. A request can be denied due to insufficient data blocks (for example, the FileFcrDeniedThreshKern column) or because there is insufficient space in the FSG cache (for example, the FileFcrDeniedCache column). The FSG subsystem can reject a request containing insufficient data blocks that the File System thought had enough blocks because the FSG subsystem reduces the count by the number of data blocks that are already resident in the cache.

FLOAT
FileFcrDeniedUser count Number of Cylinder Read requests denied by the File System.

This column records the number of Cylinder Read attempts denied by the File System. A request can be denied by the File System due to insufficient number of data blocks being requested (for example, the FileFcrDeniedThreshUser column). For information, see the FileFcrDeniedThreshUser column.

FLOAT
FileFcrDeniedThreshKern count Number of Cylinder Read requests denied by the FSG subsystem due to insufficient data blocks.

This column records the number of Cylinder Read requests denied due to the data block threshold criteria. There is a minimum threshold of data blocks for an individual Cylinder Read request. If the number of data blocks is below this threshold, the overhead of the Cylinder Read operation is considered too large and issuing individual data block reads is considered more efficient. Therefore, the Cylinder Read request is denied. FSG must reevaluate the threshold for a request that the File System considered valid since FSG eliminates any data blocks from the request list that are already resident in the cache. This could reduce the count that the File System thought was above the threshold to one that is now below.

FLOAT
FileFcrDeniedThreshUser count Number of Cylinder Read requests denied by the File System due to insufficient data blocks.

This column records the number of Cylinder Read requests denied due to the data block threshold criteria. There is a minimum threshold of data blocks for an individual Cylinder Read request. If the number of data blocks is below this threshold, the overhead of the Cylinder Read operation is considered too large and issuing individual data block reads is considered more efficient. Therefore, the Cylinder Read request is denied.

FLOAT