Goog notes on X$ tables
http://www.adp-gmbh.ch/ora/misc/x.html http://www.orafaq.com/faqdbain.htm
Histogram Overview
Histograms ========== For uniformly distributed data, the cost-based approach makes fairly accurate guesses at the cost of executing a particular statement. However, when the data is not uniformly distributed, the optimizer cannot accurately estimate the selectivity of a query. Beginning in release 7.3, for columns which do not have uniform data distribution, Oracle will allow…
To see only files and/or folders using LS command
To see only files use follwoing command. ls -l | grep -v “^d” To see only folders use follwoing command. ls -l | grep “^d”
Process Map for CPU and Memory for OS processes
Remember : 2 commands to see OS stats. (1) TOP : This command will provide following information. SIZE column display Memory allocated to this process. RES column display Actually allocated memory for the process. tuningdb21->AWRTEST@(/db1/home/oracle/paresh)top load averages: 0.17, 0.15, 0.14 10:51:36 120 processes: 119 sleeping, 1 on cpu CPU states: % idle, % user, %…
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DBMS_STATS Metalinks Notes
Note:102334.1 Subject: How to Automate Change Based Statistic Gathering – Monitoring Tables
USE_NL and INDEX hints example
select /*+ USE_NL(A,B) INDEX(a ATS_FLORIST_FITTYPE_I)*/ a.FIT_ID from ATS_FLORISTS a,ATS_FLORISTS_TRACKING b where b.FIN_PROC = ‘N’ AND b.OLD_FRESH_PAY = ‘Y’ and b.NEW_FRESH_PAY=’N’ and a.FIT_TYPE=’P’ and a.ID= b.fit_id
Index Range Scan
If your index is NONUNIQUE, you cant enforce Index Unique Scan.
SQLPLUS COPY command Precautions.
One test case today i found with copy command. When we are using sqlplus copy command with “APPEND” clause, and if source table contains any NUMBER datatype without Precision and Scale, then COPY statement fails with error indicating “NUMERIC ERROR and Number data type precision is higher than 38 digit”.
Optimizer_Index init.ora parameter explaination.
For Index ( Range Scan and Fast Full Scan Setings )in query (1) RULE uses index range scan (2) CBO uses Index fast full scan ( called Index FFS ) Here CBO uses multi block IO reading as per db_file_multi_block_read_count). By default, the CBO costs physical IO and logical IO the same. So it ignores…
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CTAS with LONG Column for 9i and higher
Executing CTAS statement having TO_LOB(LONG COLUMN). For example: create table blah as select GNT_ID.nextval, 1060 as gnt_ref_id, org.gnt_id, org.gnt_group_note, org.gnt_language, to_lob(org.gnt_text_string) as gnt_text_string, org.gnt_text_emphasize from asra_002.gnt_groupnote_txt org where org.gnt_group_note in (select gnr_note from asra_002.gnr_groupnote_ref)