IBM Informix Developer's Handbook - IBM Redbooks

If you need a secured authentication method, IBM Informix Server also has two
secured connection methods by way of the encrypted Communication Support
Module (CSM) and single password CSM. You can use one or the other, but not
both at the same time. Neither the encrypted CSM not the single password CSM
method work over multiplexed connections. Enterprise Replication (ER) and high
availability (HA) replication support encryption but not with CSM. Secure Sockets
Layer (SSL) communications are an alternative to Informix-specific encryption
CSMs. SSL encrypts data end-to-end and secures TCP/IP and Distributed
Relational Database Architecture (DRDA) connections between two points
over a network. For setup information, see the developerWorks® article Protect
your data with Secure Sockets Layer support in Informix Dynamic Server, Part 1:
Setting up SSL support in IDS, which is available at:
http://www.ibm.com/developerworks/data/library/techarticle/dm-0912securesockets1
/index.html
Programming and user process considerations
Any SQL or stored procedure call is parsed and optimized when the engine first
receives the statement. Parsing and optimization methods require a little extra
running time. If you can minimize this time, you can speed up query execution.
The following factors can speed up execution time:
► If you cannot optimize the query syntax in advance, have the DBA set the
OPTCOMPIND parameter in the onconfig file to 2 to use distribution data
(determined by Update statistics usage).
► If you can optimize all of your query syntax expressions in advance, you might
want your DBA to consider using OPTCOMPIND 1 or 2.
► If the same statement is executed multiple times, it is placed in a procedure or
dictionary cache. Cache statements run faster.
► If the statement is a prepared statement, the statement can be shared by
multiple users and does not need reparsing or optimizing.
► When a statement execution thread is ready to run, it is scheduled to run on a
CPU VP. On a system with multiple processors where each CPU VP maps to
a physical processor, multiple statements can run concurrently on multiple
CPU VPs. Take advantage of multiple CPUs whenever possible by means of
concurrent queries, parallel subqueries, and the degree of parallelism.
► When a statement runs on the CPU VP, it is given a brief block of time to run.
At the end of the time unit, it is placed into a VP wait cycle, and the next
statement thread gets a time block on the VP queue. This use of a wait cycle
gives all executing processes an opportunity to make progress, regardless of
the number of processes that are running.
Chapter 1. Introduction to IBM Informix 19