About Undocumented parameters

[shravansam]

Hai Friends,

If anybody knows & heard about the following parameters, just send your explanations(notes) and uses of that to my mailid :- shravansam@hotmail.com

1) advanced_dss_features
2) db_block_write_batch
3) db_writer_scan_depth
4) disable_logging
5) dss_cache_flush
6) lm_groups
7) log_buffers_debug
8) init_sql_file
9) trace_block_size

thanks in advance.

Regards,

saravanan.

[jmodic]

1. _ADVANCED_DSS_FEATURES
Description from x$ksppi: "enable advanced dss features"

2. DB_BLOCK_WRITE_BATCH
An ancient parameter from Oracle6, obsolete from 7.0! If its meaning is still of any use for you, here is a quote from some internal resources:
"Number of blocks to group in each DB Writer IO specifies the no of blocks to be written to the disk in one write operation. Should be increased till write wait time and write complete waits starts to increase. DBWR Free Low is the number of times DBWR is invoked because a user process found at least DB_BLOCK_WRITE_BATCH/2 buffers on the dirty list. This parameter specifies the number of blocks which should be written to disk at one time. This parameter should only be increased until the statistics Write Complete Waits and Write Wait Time show growth. Write Complete Waits is the number of times a process waited for DBWR to write a current block before making a change to a buffer."

3. _DB_WRITER_SCAN_DEPTH
Description from x$ksppi: "Number of LRU buffers for dbwr to scan when looking for dirty buffers"

4. _DISABLE_LOGGING
Description from x$ksppi: "Disable logging"
A quote from some internal resources: "If this is true, redo records will not be generated - no recovery is possible if the instance crashes. It is mainly used for getting good benchmarking results. Default is false."

My advice: Do not play with this parameter unless you can afford to loose entire database!!! In case of system crash or shutdown abort there is no way you will be able to bring database up again!

5. _DSS_CACHE_FLUSH
Description from x$ksppi: "enable full cache flush for parallel execution"

6. _LM_GROUPS
Parallel server parameter. Description from x$ksppi: "number of groups configured for the lock manager"

7. _LOG_BUFFERS_DEBUG
A quote from some internal resources: "debugging: fill redo buffers with [well known] junk after writes"
Description from x$ksppi: "debug redo buffers (slows things down)"

8. INIT_SQL_FILE
This parameter is obsolete from 7.2 on. It's purpose was to specify some other SQL script to be called implicitely when creating the database. The default was (still is) SQL.BSQ. This parameter is still available as hidden parameter _INIT_SQL_FILE.

9. _TRACE_BLOCK_SIZE
A quote from some internal resources: "This parameters is only there for debugging purposes. Customers or support will never have to use it"


[Edited by jmodic on 06-29-2001 at 11:56 AM]

[pando]

this might help, not as good as jmodic explanation but give general comments of all parameters

Run it as SYS

set pause on
select nam.ksppinm NAME,
nam.ksppdesc DESCRIPTION
from x$ksppi nam,
x$ksppsv val
where nam.indx = val.indx
order by 1
/