Rollback segments are one of those PUBLIC assets that can be somewhat of a
nightmare. While your running a simple select you may have interest in every
rollback segment in the database because of the nature of these beasts. When a
transaction modifies data the original copy of the row is held in a rollback
segment so that the transaction can rollback (hence the name). The problem that
occurs is when one transaction modifies a row in a table and your select
statement is interested in that table. Then the data in the rollback segment
MUST be held until whichever of you finishes LAST. This is how Oracle creates
it's "read consistent view" of the data. Using the SET TRANSACTION command is
really a holdback from Oracle6 where rollback segments just grew to whatever
size was allowed. Most of us had one really large segment that we used for long
running transactions that would modify a ton of data. Since Oracle7 and the
'optimal' setting on rollback segments I have not found a reason to use that
particular set transaction command. The basics are pretty simple, run
utlbstat/utlestat periodically on your DB looking at the shrinks and wraps for
each rollback segment. Then resize the segments as needed to minimize, but not
eliminate these.
Dick Goulet
____________________Reply Separator____________________
Author: [EMAIL PROTECTED]
Date: 5/9/2001 12:40 AM
Hi All,
Here is my environment;
NT v4
Db Oracle Workgroup v8.1.6
Rollback Segments
SEGMENT_NAME OWNER TABLESPACE_NAME
------------------------------ ------ ------------------------------
SYSTEM SYS SYSTEM
RBS0 PUBLIC RBS
RBS_P1 SYS RBS
RBS_P2 SYS RBS
RBS_P3 SYS RBS
RBS_P4 SYS RBS
RBS_P5 SYS RBS
Is it possible to assign one public rollback segment explicitly to one
particular transaction?
I tried using SET TRANSACTION USE ROLLBACK SEGMENT but other users I found out
can still use it. So, I guess
the best alternative is to set that RB segment to OFFLINE after using and set
ONLINE before executing the SET TRANSACTION ...
Do you know how it can be done inside Forms?
Thanks in advance!
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