SQL/MX 3.1 Installation and Management Guide (H06.23+, J06.12+)

Enhancing SQL/MX Database Performance
HP NonStop SQL/MX Release 3.1 Installation and Management Guide—663852-001
15-13
Using SCF ALTER DISK to Resize the
SQLMXBUFFER Attribute

Max denotes the maximum savepoint buffer size per volume. The value is denoted
in KB.
16 KB Blocks

Max denotes the maximum number of blocks that can be used to store savepoint
data.

In Use denotes the current number of blocks holding savepoint data.
Failures

SavePoint Limit denotes the number of failures caused because the savepoint limit
was reached. The savepoint buffer limit for a statement is 1/64th the Max
Savepoint buffer size per volume.

Buffer Full denotes the number of failures caused because the buffer limit was
reached. The buffer limit is considered reached if the total amount of savepoint
buffer data for all the statements on a volume exceeds the Max savepoint buffer
size.

Memory Pressure denotes the number of failures caused because the memory
pressure was detected.

No Memory denotes the number of failures caused because of non-availability of
physical memory for the allocation.
Using SCF ALTER DISK to Resize the SQLMXBUFFER Attribute
Use the SCF ALTER DISK command to change the size of the SQL/MX buffer on a
disk volume. For example:
SCF - T9082G02 - (04MAY04) (07APR04) - 05/12/2005 22:26:46 System \DRIS1 (C)
1986 Tandem (C) 2004 Hewlett Packard Development Company, L.P.
(Invoking \DRIS1.$SYSTEM.STARTUP.SCFCSTM)
1-> alter disk $D*,SQLMXBUFFER 128

If possible, you should always stop the affected disk volume before you alter the
SQLMXBUFFER attribute, using the STOP DISK command to put the disk in the
STOPPED state. If you cannot first stop the disk (for example, if the disk volume
contains swap files that cannot be stopped without creating problems), perform the
SCF ALTER DISK command just before system coldload to minimize or eliminate
the risks of CPU failure and configuration mismatches between primary and
backup CPUs.

The maximum size of the SQLMXBUFFER space is 768 MB, and the minimum
size is 32 MB. The default value is 128 MB. If you specify a value below the current
minimum supported size, DP2 automatically uses the current minimum value. This
minimum value might not be sufficient to perform even moderately complex
queries, so you should avoid using it unless it is appropriate. If you specify a value