README for HP Neoview Release 2.4 Service Pack 2

Neoview SQL Database
Release 2.4 SP2 introduces these new features and enhancements to the Neoview SQL database:
• “Performance Enhancements” (page 8)
• “Limiting CPU Time for a Query” (page 8)
• “Limiting Memory for a Query” (page 8)
• “Obtaining EXPLAIN Plans While Queries Are Running” (page 8)
• “Recalibrating Internal Sequence Generators” (page 9)
• “Loading Data Into an Existing Table With the LOAD IF EXISTS Option” (page 9)
Performance Enhancements
Release 2.4 SP2 introduces performance enhancements that:
• Improve throughput of the merge phase in a SORT operation when SORT overflows.
• Reduce the pathlength when evaluating expressions.
• Improve pathlength by moving data in bulk if it involves varchar and nullable columns.
• Improve the evaluation of IN lists and CASE statements.
• Improve compile time for queries that include large expressions.
Limiting CPU Time for a Query
A new threshold value limits, in seconds, the amount of CPU time that a query is allowed to use
in any one executor server process (ESP) or master process. A query is terminated and an error
is raised if any query process exceeds this threshold. By default, there is no limit. To set this
threshold, please contact your HP Support representative for assistance.
Limiting Memory for a Query
A new threshold value limits how much virtual memory, per CPU, a query can use during its
execution. The default limit is 1024 MB per CPU. This limit is distributed among the Big Memory
Operators (BMOs)—HashJoin, HashGroupBy, Sort, and MergeJoin—as quotas and among the
non-BMOs—ProbeCache, PA, Exchange, and PhysicalSequence—as the sum of their estimated
memory usage and is allocated at run time. The BMOs in all executor processes (ESP and master),
which are running on a CPU working for the query, allocate memory no greater than the memory
limit per CPU.
The CPU-based memory limit allows all queries to run reasonably well through the sharing of
the memory resource. You can control the memory limit for each query, thus improving the
concurrency and scalability of the Neoview system. Setting the memory limit to zero turns off
this feature and causes the BMOs to use a per-process quota system. To change the threshold
limit for a query or turn off the threshold limit, please contact your HP Support representative
for assistance.
Obtaining EXPLAIN Plans While Queries Are Running
Release 2.4 SP2 supports the ability to capture an EXPLAIN plan for a query at any time while
the query is running. By default, this behavior is disabled for a Neoview session. To enable this
feature, please contact your HP Support representative for assistance.
NOTE: Enable this feature before you start preparing and executing queries.
Once this feature is enabled, use the following new syntax (shown in bold below) in an EXPLAIN
statement or EXPLAIN function to get the query execution plan of a running query:
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