ALLBASE/SQL Reference Manual (36216-90216)

Chapter 2 97

Using ALLBASE/SQL

Using Multiple Connections and Transactions with Timeouts

Setting Timeout Values

Be sure to set a timeout value when using multiple connections to avoid undetected

deadlocks and undetected wait conditions. An undetected deadlock is possible when

multi-transaction mode is used in conjunction with more than one DBEnvironment with

multiple applications accessing the same DBEnvironments at the same time. An

undetected wait condition is possible when multi-transaction mode is used with multiple

connections to the same DBEnvironment within a single ISQL session or application.

A timeout value can be set with any of the following:

• START DBE

• START DBE NEW

• START DBE NEWLOG

• SQLUtil ALTDBE

• SET USER TIMEOUT

• SET SESSION USER TIMEOUT

• SET TRANSACTION USER TIMEOUT

The ﬁrst four methods provide a means of setting timeout values at the DBEnvironment

level. The SET USER TIMEOUT statement provides a way of setting transaction, session, or

application speciﬁc timeout values. The range of possible values is zero (no wait) to the

speciﬁed maximum in the DBECon ﬁle for a given DBEnvironment.

For a multi-connect application operating in multi-transaction mode, it is

essential

use the SET USER TIMEOUT statement to avoid an undetectable deadlock or wait condition.

For information regarding transaction modes, see the following section, “Setting the

Transaction Mode.”