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When you configure virtual shared memory on your system, you must decide
what portion to reserve for decision-support queries. Decision-support queries
use large amounts of the virtual portion of shared memory to perform joins
and sort operations.
Use the following parameters to control how decision-support queries are
processed and to control the amount of memory that the database server allocates
to decision-support queries. For more information about tuning these configuration
parameters, see your IBM Informix Dynamic Server Performance Guide.
| Configuration Parameter |
Description |
| DATASKIP |
Controls whether the database server skips an unavailable
table fragment. |
| DS_MAX_QUERIES |
Specifies
the maximum number of queries that can run concurrently. |
| DS_MAX_SCANS |
Limits the number of Parallel Database Query (PDQ) scan
threads that the database server can execute concurrently. |
| DS_TOTAL_MEMORY |
Specifies the amount
of memory available for PDQ queries.
Set the DS_TOTAL_MEMORY configuration
parameter to any value not greater than the quantity (SHMVIRTSIZE - 10 megabytes). |
| DS_NONPDQ_QUERY_MEM |
Enables you to increase the amount of memory that is available for
a query that is not a PDQ query. |
| MAX_PDQPRIORTY |
Limits the amount
of resources that a query can use. |
| OPTCOMPIND |
Advises the optimizer on an appropriate join strategy
for your applications. |
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