IBM 000-8697 Manual de usuario descargar pdf (Pagina 661)

100

101

Product Environment 9-41

Heuristic End-Transaction

As a consequence, the transaction remains open. The open transaction

preventsyou frombackinguplogicallogﬁlesand freeingspaceinthelogical

log. As the logical log continues to ﬁll, it might reach the point speciﬁed by

the exclusive-access, long-transaction high-water mark, LTXEHWM. If this

occurs, normal processing is suspended. At some point after the LTXEHWM

high-water mark is reached, you must decide if the open transaction is

endangering your logical log. The danger is that if the logical log ﬁlls

completely, OnLine shuts down and you must perform a data restore.

You must decide if it is right for you to kill the transaction and protect your

system against the possibility of ﬁlling the logical log, despite all the

problemsassociatedwithexecutingtbmode-Z,orifitisrightforyoutowait

and see if communication with the coordinator can be reestablished in time

to end the transaction before the logical log ﬁlls.

The tbmode -Z address command is intended for use only if communication

between the coordinator and the participant is broken. To ensure that this is

the case, the tbmode -Z command does not execute unless the database

server process that was executing the piece of work has been dead for the

amount of time speciﬁed by TXTIMEOUT. (Refer to page 9-57 for a deﬁnition

of the TXTIMEOUT conﬁguration parameter.)

The address parameter is obtained from tbstat -u output. Refer to page 9-58.

Refer to page 7-69 for additional tbmode -Z syntax information.

When you execute tbmode -Z, you direct the tbmode process to remove the

transaction entry that is located at the speciﬁed addressfrom the transaction

table. Two records are written in the logical log to document the action. The

recordsaretypeROLLBACKandENDTRANS,orifthetransactionwasalready

heuristically rolled back, ENDTRANS only. The following message is written

to the participant OnLine message log: (refer to page 8-29 for a complete

description of the message)

(time) Transaction Completed Abnormally (endtx): tx=address

flags:0xnn user username tty ttyid

Your actiontoremoveall transaction informationfromeitherthe coordinator

or the participant OnLine shared memory breaks the two-phase commit

protocol.

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