IBM 000-8697 Uživatelský manuál stáhnout pdf (Strana 675)

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Product Environment 9-55

Determining Database Consistency

You can also use the information in the HEURTX log record to locate all log

records (at all participating OnLine database servers) associated with the

global transaction of which this local transaction is just a piece. The steps

involved are as follows:

1. Obtain the local xid from the HEURTX log record at a participant

OnLine where the transaction rolled back.

2. LookforaPREPARE logrecordforthatlocalxidandobtaintheglobal

transaction number (GTRID) and the name of the coordinating

OnLine. (Refer to page 9-58 for more information about the GTRID.)

3. Examine the logical log maintained by the coordinator OnLine and

locate the BEGPREP record for this global transaction.

4. Read the BEGPREP log record and obtain the coordinator’s local xid

for the transaction.

5. ReadthelonglistingoftheBEGPREPrecordtoobtainalistofallother

participants.

6. At eachparticipant OnLine,read the logical logto ﬁndthe PREPARE

record that contains the GTRID associated with this transaction and

obtain the local xid for the piece of work performed by this

participant.

7. At each participant OnLine, use the local xid to locate all logical log

records associated with this transaction (committed or rolled back).

8. Use the records you ﬁnd and your knowledge of the application to

help you construct a compensating transactionthat either rolls back

the committed effects of the transaction or commits the pieces of

work that were rolled back.

Example Manual Recovery

This example is intended to illustrate the kind of work that is involved in

manualrecovery.ThefollowingSQLstatementswereexecutedbyuserpault.

Error -698 was returned.

<prompt> dbaccess

CREATE DATABASE tmp WITH LOG;

CREATE TABLE t ( a int);

CLOSE DATABASE;

CREATE DATABASE tmp@apex WITH LOG;

CREATE TABLE t ( a int);

CLOSE DATABASE;

1 2 ... 670 671 672 673 674 675 676 677 678 679 680 ... 701 702

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