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.
Thetransaction table specifically supports the X/Open environment, in which
theconcept of a global transaction replaces the traditional UNIX architecture
of one application tool process associated with one database server process.
Ina global transaction, more than one database server process can be enlisted
to perform work on behalf of a single application tool process. That is, the
transactionbecomes the central structure instead of the user process. Support
for the X/Open environment requiresIBM Informix TP/XA.
Within the OnLine environment, the concept of transaction has been added
tothe traditional UNIX architecture. Each OnLine transaction is considered to
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.Tracking information derived from both the transaction and user tables
appearsin the tbstat -u display, although the information is organized a little
differently.For further information about using the tbstat -u display to track
transactions, refer topage 9-58.
OnLine User Table
The user table tracks all processes that attach to shared memory.
EveryOnLine database server maintains at least two entries in the user table
while running. The first entry in the user table is reserved fortbinit, the
masterdaemon. The second entry in the user table is reserved for tbundo, the
daemon process that is responsible for rolling back transactions associated
with a process that has died prematurely or has been killed. Thetbundo
daemonis forked from tbinit.InUNIXsystems that do not allow processes to
be renamed, thetbundo daemon appears as a second tbinit daemon.
In the user table, and in tbstat -u output, the process ID for thetbundo
daemon displays as 0 until the process is actually needed. Whentbundo is
started, the actual user process ID is used.
Thenext entries in the user table belong to the page-cleaner daemons, tbpgcl,
if any daemons are specified.
The database server processes currently running are the next entries.