NonStop SQL/MP Reference Manual

NonStop SQL/MP Reference Manual—142115
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=_SQL_CMP_DOUBLE_SBB_OFF DEFINE
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Availability of CPUs at compile time
When you compile a parallel query, the compiler assigns ESPs to the CPUs
specified as available in =_SQL_CMP_CPUS_node. If a CPU is unavailable when
you compile the query then no ESP is assigned to that CPU, even if you specified
the CPU as available in this DEFINE. In this case, the executor chooses a substitute
CPU for the stranded ESP. The substitute CPU does not have to be specified as
available in =_SQL_CMP_CPUS_node.
=_SQL_CMP_DOUBLE_SBB_OFF DEFINE
=_SQL_CMP_DOUBLE_SBB_OFF is a system DEFINE that directs SQL not to use
file system double buffering.
filename
must be a legal Guardian file name but has no purpose except to make the ADD
DEFINE command syntactically correct.
Considerations—=_SQL_CMP_DOUBLE_SBB_OFF
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=_SQL_CMP_DOUBLE_SBB_OFF disables file system double buffering for
queries that are SQL compiled while this DEFINE is in effect.
See the NonStop SQL/MP Installation and Management Guide for a full discussion
of how to manage double buffering.
=_SQL_CMP_DOUBLE_SBB_ON DEFINE
=_SQL_CMP_DOUBLE_SBB_ON is a system DEFINE that directs SQL to use file
system double buffering to scan the inner table in a nested join or key-sequenced merge
join.
filename
must be a legal Guardian file name but has no purpose except to make the ADD
DEFINE command syntactically correct.
Considerations—=_SQL_CMP_DOUBLE_SBB_ON
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By default, the SQL optimizer considers using file system double buffering for scans
that use VSBB and BROWSE ACCESS except for an inner scan of a nested join or
key-sequenced merge join. When the =_SQL_CMP_DOUBLE_SBB_ON DEFINE
ADD DEFINE =_SQL_CMP_DOUBLE_SBB_OFF, CLASS MAP,
FILE filename
ADD DEFINE =_SQL_CMP_DOUBLE_SBB_ON, CLASS MAP,
FILE filename