Informix database isolation level

Isolation level

The default isolation level is based on whether or not the database has transaction logging enabled, and whether or not it is ANSI-compliant. The info in this link is summarized below:

Informix Name ANSI Name When This Is the Default Level of Isolation
Dirty Read Read Uncommitted Database without transaction logging
Committed Read Read Committed Databases with logging that are not ANSI- compliant
Repeatable Read Serializable ANSI-compliant databases

ANSI compliance

How do you know if your database is ANSI-compliant or not. There must be an explicit way of finding this out, but I don’t know it. However, there are a couple of empirical ways of finding out:

  1. Non ANSI-compliant databases quietly truncate text that is longer than the size of the associated CHAR, VARCHAR, etc, column.
  2. For an ANSI-compliant database you cannot change the logging mode to buffered logging, or turn logging off.

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