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.
Setting NUMBUFG
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.