NUMBUFG parameter

Number of above-the-bar buffers

Summary

Default value

0

Parameter type

System

Where set

Not resettable

Related products

All

Introduced

Model 204 V7.1

Description

Allocate this number of buffer pool buffers above the bar (ATB).

• Prior to version 7.7 of Model 204:

  NUMBUFG specifies the number of buffer pool buffers built ATB, while the number of buffer pool buffers built BTB is based on the setting of MINBUF, MAXBUF, and SPCORE.

• As of version 7.7:

  If NUMBUFG is specified, no buffer pool buffers are built BTB; all buffers are ATB. Model 204 obtains exactly the NUMBUFG number of buffers.

  In this case, NUMBUFG essentially replaces the BTB parameters: NUMBUF and MINBUF are automatically reset to 0, and MAXBUF and SPCORE are ignored.

The maximum number of buffers is 2**31/3, or 715,827,882, which limits buffer pools to 4.2 terabytes or less.

The minimum number of ATB buffers is:

NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15)

If you set NUMBUFG to a value lower than the minimum, the value is reset to the calculated value and you receive messages like the following:

*** M204.2756: NUMBUFG reset to NLRUQG * ((NSERVS + NSUBTKS) * MAXOBUF + 15) = 1 * ((2+9) * 4 + 15) = 59 *** M204.0075: Initialization completed. Buffers = 0+59

If you set NUMBUFG greater than 0, the X'02' bit of the XMEMOPT parameter (the default), must also be set.

See also

For more information about setting NUMBUFG, see Using 64-bit addressing and Above the Bar (ATB) storage.