| Parameter | Specify . . . | Minimum | Maximum | Default |
|---|---|---|---|---|
| PREFSBL | the prefetch buffer length for one prefetch. | 1024 | 65535 | 3000 |
The PREFSBL parameter specifies the size of the buffer for a single prefetch, which determines how much record data is prefetched. See also the description of the PREFTBL parameter, which specifies the total buffer space used by prefetch/multifetch.
When prefetch or multifetch is active, Adabas makes a buffer available to the user program for storing prefetched records. If a required record is already in a prefetch buffer, the record is taken directly from the buffer. PREFSBL specifies the size of this buffer.
Note:
Do not specify this operand unless PREFETCH=YES or PREFETCH=OLD also
is specified.
The following formula can be used to estimate the initial size of PREFSBL:
300 + FBL + 2 * (16 + RBL) + 2 * ((16 + RBL) * recs) = PREFSBL
In this calculation, FBL is the length of the format buffer, RBL is the length of the record buffer, and recs is the number of records per call.
For long sequential processes, this parameter should be as large as possible unless the sequential processes are frequently interrupted with "value start" (L3/L6) or RC commands; in that case, a large value often causes records to be prefetched needlessly.
Execute a user program using multifetch. Use a 15,000-byte prefetch buffer.
ADARUN PROG=USER,PREFETCH=YES,PREFSBL=15000
