IBM 000-8697 User Manual

IBM Informix OnLine Database Server Administrator’s Guide

The default value of

DEADLOCK_TIMEOUT

 is 60 seconds. Adjust this value

carefully. If you set it too low, individual OnLine database servers abort
transactions that are not deadlocks. If you set it too high, multiserver
deadlocks could reduce concurrency.

The configuration

TXTIMEOUT

 is specific to

IBM I

nformix

STAR

 two-phase

commit protocol. It is only used if communication between a transaction
coordinator and participant has been interrupted and needs to be
reestablished.

The function of

TXTIMEOUT

 is to specify a period of time that a participant

OnLine waits to receive a commit instruction from a coordinator OnLine
during a distributed transaction. If the period of time specified by

TXTIMEOUT

 elapses, the participant OnLine checks the status of the trans-

action to determine if the participant should initiate automatic participant
recovery.

TXTIMEOUT is specified in seconds. The default value is 300 (five minutes).
The optimal value for this parameter varies, depending on your specific
environment and application. Before setting this parameter, read the
discussion that begins on

.

The multiserver update capability supported by

IBM I

nformix

STAR

requires

an enhanced tbstat -u output that can track both users and transactions. In
the

IBM I

nformix

STAR

 environment, relationships among users, transac-

tions, and locks (and other shared-memory resources) must be explicitly
described as follows:

■

Locks are owned by transactions, not by database server processes.

■

Transactions are usually owned by a database server process.

■

A transaction can be orphaned and exist without being owned by a
database server process.

The transactions section of the tbstat -u output supports this level of
description. Each tbstat -u transactions field is explained in this section.