IBM 000-8697 Manual Do Utilizador
2-158
IBM Informix OnLine Database Server Administrator’s Guide
Blobspace Logging
The duration of a transaction is a key variable that might be beyond your
control. An application that does not require much space for logical log
records might generate long transaction errors if the users permit transac-
tions to remain open for long periods of time. The more logical log space is
available, the longer a transaction may be permitted to remain open before a
long-transaction error condition develops. (Refer to
control. An application that does not require much space for logical log
records might generate long transaction errors if the users permit transac-
tions to remain open for long periods of time. The more logical log space is
available, the longer a transaction may be permitted to remain open before a
long-transaction error condition develops. (Refer to
information about long transactions.)
The amount of
CPU
activity can affect the ability of OnLine server processes
to complete the transaction. Repeated writes to the logical log file increase the
amount of
amount of
CPU
time each server process needs to complete the transaction.
Increased logical log activity can imply increased contention of logical log
locks and latches as well. (This is the reason you might want to move your
logical log files from the root dbspace to another, less active, dbspace.)
locks and latches as well. (This is the reason you might want to move your
logical log files from the root dbspace to another, less active, dbspace.)
The frequency of rollbacks affects the rate at which the logical log fills. The
rollbacks themselves require logical log file space, although the rollback
records are small. In addition, rollbacks increase the activity in the logical log.
rollbacks themselves require logical log file space, although the rollback
records are small. In addition, rollbacks increase the activity in the logical log.
The number of logical log files affects the frequency of logical log backups
and, consequently, the rate at which blobspace blobpages can be reclaimed.
Blobspace blobpages emptied after a
and, consequently, the rate at which blobspace blobpages can be reclaimed.
Blobspace blobpages emptied after a
DELETE
statement cannot be freed for
use by other blobs until the log file in which the
DELETE
statement is occurs
is freed.
Blobspace Logging
OnLine uses the information that is stored in the logical log to help it track
and log blobs stored in a blobspace. This creates some cause-and-effect
relationships that may not be immediately obvious to the administrator. The
method that OnLine uses to log blobspace blobs is described on
and log blobs stored in a blobspace. This creates some cause-and-effect
relationships that may not be immediately obvious to the administrator. The
method that OnLine uses to log blobspace blobs is described on
.
(To compare blobspace logging to dbspace logging, refer to
for an
overview, and
for description of what happens during dbspace
logging.) The paragraphs that follow highlight the interaction between the
logical logs and management of blobspace blobs.
logical logs and management of blobspace blobs.
The status of a logical log can affect the availability of disk space in
blobspaces. Even after a transaction that deleted blobs is committed, the
blobspace blobpages that stored those blobs are not marked as free until the
logical log file containing the transaction record is marked as free.
blobspaces. Even after a transaction that deleted blobs is committed, the
blobspace blobpages that stored those blobs are not marked as free until the
logical log file containing the transaction record is marked as free.