Kbase 17955: Use of the -i Option and its True Effect on the BI File
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
5/19/1998 |
|
Use of the -i Option and its True Effect on the BI File
The -i startup parameter tells Progress to run without using database
integrity or recovery. We basically do not advise customers to use
this option unless absolutely necessary because if the system fails
why the database is running in no integrity mode, there is no chance
for recovery without restoring from a backup.
So the question is what could we possibly gain by using this option if
it eliminates our ability to recover from a crash situation? The
answer is performance. When we run with -i, we are actully writing
fewer data and bi blocks out to disk. For larger procedures that
create and delete large numbers of records thus require alot of i/o
overhead, we can eliminate a fair amount of the i/o with the -i. A
couple of examples of such operations would be loading a database for
the first time, or using the bulkloader. The number of disk i/o
operations can be reduced significantly for such procedures.
One caveat to this (besides the obvious one of no recoverability) is
that using -i still supports undo loging, which is the ability to
reverse the effects of a transaction that has not yet been committed.
With undo logging, the database manager reads all the log records
generated by the transaction in reverse order all the way back to
where it began. This is documented extensively in KB13866 Undo and
Redo Logging:How the BI file works.
What this all means is that we may not gain all the we anticipated by
using the -i option in regards to growth of the bi file. One creative
use of the -i that has recently been brought to our attention is using
it to guard against excessive bi growth, hence lowering the risk of
the bi hitting the 2 gig file size limitation. Or to take it one step
further, one could theoretically use the -i to save file system space
where the bi file resides,however NONE of this supported by Progress
Technical Support.
The reason why the uses of -i in the previous paragraph are completely
erroneous is due to the redo logging. Redo logging WILL cause the bi
file to grow, especially during large transactions. It is critical to
understand this concept, as failure to do so could result in a truly
unrecoverable situation. The bi file WILL grow even if the -i is
enabled. There are no benchmarks or percentages to be offered for
size differences between bi files from db's using the -i versus those
that are not. Nor can this option be used to run transactions that
are poorly scoped.
NOTE: Although you may experience reduced bi file growth, your
mileage may vary and this is not a supported tool for manipulating
growth of the bi file.
SDA 5/19/98