| Parameter | Specify . . . | Possible Values | Default |
|---|---|---|---|
| PREFETCH | whether to enable a prefetch option automatically. | YES | OLD | NO | NO |
This parameter determines whether the Adabas prefetch feature is enabled automatically; if it is, execution is transparent to the user program.
There are two Adabas prefetch options: the multifetch option is supported across Adabas platforms; the prefetch option is available only on mainframe Adabas. For information about these two options, see the Adabas Command Reference documentation.
Records can be prefetched and stored in a prefetch buffer for the following commands:
L1/L4 with I or N option (read by ISN, find with GETNEXT)
L2/L5 (read physical)
L3/L6 (read logical by descriptor)
L9 (histogram)
Sequential commands of the types listed above can retrieve the next record from the prefetch buffer, which saves cross-region/cross-network calls to the nucleus.
The PREFETCH parameter has the following values:
| Value | Meaning |
|---|---|
| YES | Adabas enables the command-level multifetch (M) option. |
| OLD | Adabas enables the command-level prefetch (P) option. |
| NO | Adabas does not enable the prefetch feature. |
Note:
Specify PREFETCH=YES or PREFETCH=OLD only when MODE=MULTI (multiuser
mode). Do not specify these settings when running Adabas utilities. Dynamic
reversal of read direction for L3/L6/L9 is not supported with these
settings.
Execute a user program using multifetch.
ADARUN PROG=USER,PREFETCH=YES
Execute a user program using prefetch.
ADARUN PROG=USER,PREFETCH=OLD
