Use this command to change buffer ratios, reserve chain sizes, and define
the buffer reuse threshold value for virtual file access (VFA).
Requirements and Restrictions
You can enter this command only for the basic subsystem (BSS).
Format
Notes:
- You can also separate the parameters with the , character.
- RAT381
- defines the 381 VFA buffer ratio.
- RAT1055
- defines the 1055 VFA buffer ratio.
- RAT4095
- defines the 4095 VFA buffer ratio.
- buffer
- is a buffer ratio from 1-999.
- RES381
- defines the reserve chain size for the 381 VFA buffer.
- RES1055
- defines the reserve chain size for the 1055 VFA buffer.
- RES4095
- defines the reserve chain size for the 4095 VFA buffer.
- chain
- is a reserve chain size percentage from 1-99. The reserve
chain destages the VFA buffers that are delay file pending before the buffers
are needed by VFA for new records.
The recommended values are:
- 5 percent for a production system
- 10 percent for a test system.
- Count-threshold
- defines the buffer reuse threshold value, where threshold is a
value from 1-999.
Additional Information
- Online help information is available for this command. To display
the help information, enter one of the following:
ZVFAC HELP
ZVFAC ?
- Specify only the parameters that you want to change. If you do not
specify a parameter, it retains its current value.
- The value specified for the COUNT parameter takes effect
immediately. All other values do not take effect until the TPF system
rebuilds the VFA area.
- You can abbreviate the parameters to the first 4 characters. For
example, you can enter RAT1055 as RAT1.
- The buffer values are stored in keypoint record A (CTKA).
Examples
The buffer ratios, reserve chain sizes, and the reuse threshold value are
changed in the following example.
+--------------------------------------------------------------------------------+
|User: ZVFAC DEF RAT1-10 RAT3-5 RAT4-3 RES1-5 RES3-10 RES4-15 C-36 |
| |
|System: VFAC0006I 13.12.15 VFA KEYPOINT VALUES ARE: |
| RAT1055- 10, RAT381- 5, RAT4095- 3 |
| RES1055- 5, RES381- 10, RES4095- 15 |
| COUNT- 36 |
| CURRENT VFA VALUES ARE: |
| RAT1055- 1, RAT381- 1, RAT4096- 1 |
| RES1055- 20, RES381- 20, RES4096- 20 |
| COUNT- 36 |
+--------------------------------------------------------------------------------+
Related Information
See TPF Database Reference for more information
about VFA, buffer ratios, reserve chain sizes, and the reuse threshold
value.