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  • 0 posts edited
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  • 43 votes cast
Feb
3
comment Oracle over-indexed tables
Too many indexes can cause problems with exec plan stability. .i.e. you may face problems, when Oracle suddenly "change exec plan without warning". It can also be sign, that there were performance problems in the past and somebody tried to fix them, without knowing what exactly is going on.
Feb
1
awarded  Yearling
Jan
29
comment How to run an exe from an oracle trigger
Maybe of topic. Do you really need it? May it would be better if you submitted job or AT message, and exe file was executed asynchronously.
Jan
6
comment Oracle, Cursor_Sharing = Force and Queries with literal comparisons forcing FTS
sharing was supposed to improve the performance. But now you face the negative impact of this "improvement". The best thing you can do is to contact the software vendor.
Jan
6
comment Oracle, Cursor_Sharing = Force and Queries with literal comparisons forcing FTS
Theoretically the predicate 'a' = 'b' (or 'a' = 'a' ) could be elimanated as tautology at early stage of the parsing. But it looks like the bind variable replacement (cursor sharing) takes place before. You can not do too much with that. Google the terms "bind variable peeking" and "SQL plan baseline". The most important rule for you is that a single sql_id (a sql statement hash) can have only one execution plan. The whole idea with the 'or' predicate is sick. You WANT full table scan if this predicate evaluates to true, while you want index access when it evalutates to false. IMHO the cursor
Nov
12
comment Unable to turn off automatic memory management (AMM)
You stored our changes into spifile, but you use initdev12.ora to start the database. What is in this file?
Nov
2
comment adrci not purge trace files and alert logs
AFAIK alert log and listener.log can not be managed by adrci
Oct
27
comment Select performance problems with conditional index vs non-conditional on large volume table
Try to execute the query with gather_stats hint and then use dbms_xplan to show execution plan. This might give you some numbers describing how your query is evaluated in reality.
Oct
27
awarded  Custodian
Oct
27
reviewed Approve Is Overwriting the PFILE with the database on dangerous?
Oct
26
comment Select performance problems with conditional index vs non-conditional on large volume table
What is the exec plan? Index range scan or fast full scan? Do you have a license for real time SQL monitoring? Did you try to execute the query with gather_stats hint?
Oct
26
answered Is Overwriting the PFILE with the database on dangerous?
Oct
21
comment How to optimize very slow SELECT with LEFT JOINs over big tables
OT: isn't it strange that you use LIMIT withour ORDER BY? This will return some random 100000 rows?
Oct
9
comment How to change dbid in oracle to specific value?
AFAIK the order should be execute rman; set dbid; connect target / catalog ...; restore controlfile; startup mount;. The DBID must not be read from controlfile.
Oct
8
comment How to change dbid in oracle to specific value?
Why do you need it? You can use set dbid command in rman, but this will apply only for a session. This is usually needed for cross-site restores.
Sep
16
comment Will inserting a row keep it in the buffer cache
There are some articles about buffer cache topology. When simplified, you can say it is a hash table with linked lists of pages. LRU algorithm is applied on these lists. Under some circumstances Oracle might decide to put our page on the end of the LRU list. To prevent buffer cache from starving out. There is a book from Jonathan Lewis where this is described.
Sep
16
comment Will inserting a row keep it in the buffer cache
Yes - unless using direct path insert.
Aug
25
comment Opening an Oracle database with a corrupted redo log
There are ways how to bypass media recovery phase, and open an inconsistent database. But this is beyond SO questions. You should contact Oracle support.
Aug
3
comment Oracle data dictionary, tell built-in roles apart from custom roles
there is a note on Metalink describing list of all Oracle's build-in usernames and roles.
Jul
27
awarded  Caucus