IBM 000-8697 User Manual

IBM Informix OnLine Database Server Administrator’s Guide

DB-M

onitor does not prompt for this value during initialization. You can tune

this parameter to affect performance. Refer to

.

LTXHWM

specifies the “long transaction high-water mark.” In the logical log,

LTXHWM

 is the percentage of available logical log space that, when filled,

triggers the tbinit daemon to check for long transactions. If a long transaction
is found, the transaction is aborted and the executing OnLine database server
process rolls back all modifications associated with this transaction.

The default value for

LTXHWM

is 50 percent. This means that up to 50 percent

of the available log space can be spanned by one user's transaction. When this
level is exceeded, the OnLine database server process is signalled to immedi-
ately roll back that transaction. The rollback procedure continues to generate
logical log records, however, so the logical log continues to fill. This is the
reason for the

LTXEHWM

 parameter.

DB-M

onitor does not prompt for this value during initialization. Refer to

 for more information about

LTXHWM

.

LTXEHWM

 specifies the “long transaction, exclusive access, high-water

mark.” The

LTXEHWM

 must be a higher percentage than the

LTXHWM

percentage. If the logical logs fill to

LTXEHWM

, the long transaction currently

being rolled back (refer to

LTXHWM

) is given “exclusive” access to the logical

log. The term “exclusive” is not entirely accurate. Most OnLine activity is
suspended until the transaction has completed its rollback, but transactions
that are in the process of rolling back or committing retain access to the
logical log.

The default value for

LTXEHWM

is 60 percent.

DB-M

onitor does not prompt for this value during initialization. Refer to

 for more information about

LTXEHWM

.