NonStop SQL/MP Reference Manual

NonStop SQL/MP Reference Manual—142115
Z-14
Considerations—=_SQL_cmp_node
Considerations—=_SQL_cmp_node
•
You can use a =_SQL_cmp_node DEFINE only if you are logged on as a user in
group 255. SQL ignores the DEFINE for other users.
•
If the DEFINE =_SQL_CI2_node is in effect during INITIALIZE SQL, the
alternate file specified is the file compiled and registered in the system catalog by
the INITIALIZE SQL operation.
Specifying an appropriate alternate CI2 file at initialization time is the way you
install a licensed SQLCI2.
Examples—=_SQL_cmp_node
•
The following TACL commands add two =_SQL_cmp_node DEFINES:
37> SET DEFINE CLASS MAP
38> ADD DEFINE =_SQL_CMP_SYS1, FILE
\SYS1.$VOL1.SYSTEM.SQLCOMP
38> ADD DEFINE =_SQL_CI2_SYS1, FILE
\SYS1.$VOL1.SYSTEM.SQLCI2L
=_SQL_EXE_DOUBLE_SHUTOFF DEFINE
=_SQL_EXE_DOUBLE_SHUTOFF is a system DEFINE that directs SQL to disable
file system double buffering when a specified level of memory use is reached.
Xn
is the letter X (uppercase) followed by a number from 0 (zero) through 10 that
specifies tenths of the process file segment (PFS). It represents the limit above
which double buffering is not used. If this limit is reached, double buffering is shut
off for that query. No notification is given that this has occurred. If the PFS load
decreases, double buffering is turned on again for a new query. When n is zero, the
executor never uses double buffering.
Considerations—=_SQL_EXE_DOUBLE_SHUTOFF
•
When you increase the memory use threshold, you increase the use of double
buffering but also increase the likelihood of a PFS memory overflow.
•
If the DEFINE is absent, the PFS memory-use threshold defaults to 70 percent.
•
See the NonStop SQL/MP Installation and Management Guide for a full discussion
of how to manage double buffering.
ADD DEFINE =_SQL_EXE_DOUBLE_SHUTOFF, CLASS MAP, FILE Xn