TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)
682 AppendixH
TurboIMAGE/XL versus TurboIMAGE/V
Moving from MPE/iX to MPE V
Buffer Specifications
For databases that will be moved to MPE V, the DBUTIL >>SET command can be used to
specify the number of input/output buffers to be allocated by TurboIMAGE/V in the
Database Buffer Area Control Block (DBB) depending on the number of users concurrently
accessing the database. The syntax of this command follows:
>>SET
database name
[/
maint word
] { BUFFSPECS=
num buffers
(from-users/to-users)
[
,num buffers(from-users/to-users)
] ... }
For a complete syntax listing of the DBUTIL >>SET command, refer to Chapter 8.
Parameters
BUFFSPECS is for MPE V compatibility only, because the TurboIMAGE/XL buffer
specifications are fixed at a large default value. For databases that will be
moved to MPE V, it sets the number of buffers to be allocated by
TurboIMAGE/V in the Database Buffer Area Control Block (DBB). The
following parameters are used with the
BUFFSPECS
parameter:
num buffers
is the number of buffers for the range of users specified
between the parentheses that follow. The minimum
number of buffers allowed is 5 and the maximum is 255.
The number of buffers allocated and the actual amount of
performance increase obtained depends on whether ILR is
enabled, how many users are accessing the database, the
amount of main memory available, and many other
factors.
from-users
is the minimum number of concurrent users (access paths)
for which the preceding num buffers should be allocated.
The minimum from-users value allowed is 1 and the
maximum is 120. The value must be less than the
immediately following to-users value.
to-users
is the maximum number of concurrent users for which the
preceding num buffers should be allocated. The minimum
to-users value allowed is 1 and the maximum is 120. The
value must be greater than the immediately preceding
from-users value.
Discussion
The following BUFFSPECS discussion is for databases that will be moved to MPE V. The
buffer specifications are fixed at 1280 on TurboIMAGE/XL.
The from-users and to-users counts can be the same. For example:
SET ORDERS/SELL BUFFSPECS=10(4/4)
is valid. The value of from-users must be less than or equal to the value of to-users. In
addition, the from-users/to-users ranges must be specified in increasing order. The ranges
may not overlap but they need not be consecutive. If num buffers is not specified for a