LDKBMWNG parameter

# of pages in DKBM-ATB anticipatory write window

Summary

Default value

At V7.4, either 3, or the value of LDKBMWND, if set. From V7.5 onwards the default value is set to a minimum of 0.5 * NUMBUFG. NUMBUFG will first be adjusted (rounded up) to be an even multiple of NLRUQG. Following that, if a value for LDKBMWNG is specified in CCAIN and that value is greater than .5*NUMBUFG, the value may still be adjusted:

The final value must be an even multiple of NLRUQG

The final value must not be greater than NUMBUFG minus the total number of buffers that might possibly be open at any one time: i.e NUMBUFG - (((NSERVS+NSUBTKS)*MAXOBUF)+14)*NLRUQG

Parameter type

System

Where set

On User 0's parameter line by system manager

Related products

All

Introduced

Model 204 V7.4

Description

An anticipatory write window that starts writes for any modified buffers that enter the window

When an anticipatory write for a modified buffer completes, the buffer is immediately reusable.

If NLRUQG is set greater than 1, then the value of LDKBMWNG is rounded up to a multiple of NLRUQG. LDKBMWNG has a minimum size of one (1).

High values of LDKBMWNG might unnecessarily increase the number of writes done (measured by the DKWR statistic). Low values might cause excessive waiting for buffers (measured by the DKSWAIT statistic).

Refer to Disk buffer monitor statistics and parameters and Managing ATB storage with NUMBUFG for more information.