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Using _disable_logging for PUT
Tip-No.: 2945 ( INFO2945 )

Short text

Using _disable_logging for PUT
Tip-No.: 2945

Symptom

Performance of PUT.

Cause

Performance of PUT.

Solution

**************************************************************
Using _disable_logging often leads to problems
(see Internal Message I R/3 01121).

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Tuning of DB for import with _disable_logging
----------------------------------------------

In ORACLE, the logging mechanism can be switched off using an unsupport-
ed init.ora parameter.

Advantages
Because no redo-logs are written (and thus also no archiving is perform-
ed by the archive process), the data base is approx. 3 to 5 times
faster.

Disadvantages.

By deactivating the redo mechanism, no instance recovery is possible.

Examples:

Error: ORA-1547 occurs during the import
Effect: None. There is no accessing of the redo logs, it is irrelev-
ant whether _disable_logging is activated or not.

Error: Power failure during the import
or
DB crashes.
Effect: New import is imperative (drop_1.sql)



Procedure for activation of _disable_logging:
---------------------------------------------

1. As user system, force a log-switch:
"alter system switch logfile"
2. Modification of init.ora (make note of old values|)
_disable_logging = TRUE
sort_area_size = 8388608
db_file_multiblock_read_count = 64
3. DB restart (to activate the new parameters)
4. Import
5. Re-set the changed init.ora parameters to original values
6. Restart DB in order to activate old values
7. Check whether_disable_logging is deactivated:
a. sqlplus sys/change_on_install
select ksppinm, ksppivl from x$ksppi
where ksppinm like '%dis%';
_disable_logging = FALSE should be displayed
b. Force a log-switch
The time stamp of redo-log files must change.
The archive prozess must write a new archive file.
Both checks must be performed.

10. Save the data.