IBM 000-8697 Bedienungsanleitung PDF herunterladen (Seite 148)

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2-54 IBM Informix OnLine Database Server Administrator’s Guide

Shared-Memory Internal Tables

OnLine Transaction Table

The transaction table tracks all transactions in the OnLine system.

Thetransactiontablespeciﬁcallysupportsthe

X/Openenvironment,inwhich

the concept of a global transaction replaces thetraditional UNIX architecture

of one application tool process associated with one database server process.

Inaglobaltransaction,morethanonedatabaseserverprocesscanbeenlisted

to perform work on behalf of a single application tool process. That is, the

transactionbecomesthecentralstructureinsteadoftheuserprocess.Support

for the X/Open environment requires IBM Informix TP/XA.

Within the OnLine environment, the concept of transaction has been added

tothetraditionalUNIX architecture.EachOnLinetransactionisconsideredto

be associated with a single user process. Some information that had been

tracked in the user table in earlier releases is now tracked in the transaction

table.Trackinginformationderivedfromboththetransactionandusertables

appearsinthetbstat -u display,although the information is organizedalittle

differently. For further information about using the tbstat -u display to track

transactions, refer to page 9-58.

OnLine User Table

The user table tracks all processes that attach to shared memory.

Every OnLine databaseserver maintains atleast two entries inthe user table

while running. The ﬁrst entry in the user table is reserved for tbinit, the

masterdaemon.Thesecondentryintheusertableisreservedfortbundo,the

daemon process that is responsible for rolling back transactions associated

with a process that has died prematurely or has been killed. The tbundo

daemonisforkedfromtbinit.InUNIXsystems that do not allow processesto

be renamed, the tbundo daemon appears as a second tbinit daemon.

In the user table, and in tbstat -u output, the process ID for the tbundo

daemon displays as 0 until the process is actually needed. When tbundo is

started, the actual user process ID is used.

Thenextentriesintheusertablebelongtothepage-cleanerdaemons,tbpgcl,

if any daemons are speciﬁed.

The database server processes currently running are the next entries.

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