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Clustering Factor and it’s effect on non-assm and assm tablespace. The clustering factor is a measure of the ordernesss of an index in comparison to the table that it is based on. It is used to check the cost of a table lookup following an index access (multiplying the clustering factor by the index’s selectivity gives you the cost of […]
A. B-Tree Indexes I have discussed more details in the below blog. http://clouddba.co/index-internal-oracle-using-simple-test-case/ B.Invisible Indexes Deciding which columns to index is hard. The primary key is automatically indexed, the foreign keys should also be indexed, but then what? Even more difficult is deciding which index to remove that might be a bad index. Every time a record is inserted, all […]
Index internal oracle using simple test case First of all I will create a table with char(1000) so that in one block I can fit 6-7 entries . Here are some relevant notes regarding Index split For Leaf block kdxlespl: bytes of uncommitted data at time of block split that have been cleaned out kdxlende: number of deleted entries kdxlenxt: […]
How histogram can affect query plan change hence performance. 1.Let me create a test case.I am loading the table with following distribution.Obviously it means data is somewhat skewed. Value:-1 Range:-10 Value:-2 Range:-100 Value:-3 Range:-1000 Value:-4 Range:-10000 Value:-5 Range:-100000 C##TEST@TESTDB1> create table tt1(c1 number,c2 char(10)); Table created. C##TEST@TESTDB1> declare begin for j in 1..10 loop 2 3 4 insert into tt1 […]
1.Let us create a test case first:- oracle@TST:TESTDB1[/home/oracle]$ sqlplus c##test/test C##TEST@TESTDB1> create table mytst1 as select * from dba_objects; Table created. C##TEST@TESTDB1> create table mytst2 as select * from dba_objects where rownum<5000; Table created. 2.Let us see what application executes SQL query and complaining poor performance select a.owner,a.OBJECT_NAME,a.OBJECT_TYPE,b.STATUS from mytst1 a,mytst2 b where a.OBJECT_ID=b.OBJECT_ID and b.OBJECT_NAME=’DBA_TABLES’; 3.Now create an index […]
1. On the source node to target node, create a copy of the Oracle Grid Infrastructure home. For example, as root on Linux systems, run the cp command:- # cp -prf root@rac1:/u01/app/product/12.1.0/grid/* root@rac2:/u01/app/product/12.1.0/grid 2. Delete unnecessary files from the copy.The Oracle Grid Infrastructure home contains files that are relevant only to the source node, so you can remove the unnecessary […]
Introduction This document will help to guide you for installation of Oracle 12cR1 RAC Flex cluster infrastructure on Virtual Box which is very popular because of shared storage simulation feature. Below is overall requirement in nut-shell. We need 3 servers for now.I will install RAC on First 2 servers and 3rd server will act as DNS server.My desktop RAM is […]
A.Very useful method to upgrade 11gR2 to 12c using transportable=always Full transportable export/import is a new feature in Oracle Database 12c that greatly simplifies the process of database migration. Combining the ease of use of Oracle Data Pump with the performance of transportable tablespaces, full transportable export/import gives you the ability to upgrade or migrate to Oracle Database 12c in […]
Oracle Database Audit using SYSLOG to capture Oracle Database can be configured to log events into a database table, XML files or syslog. To configure Oracle Database to log events using syslog: Configure SYSLOG 1. Execute the following commands: mkdir -p /var/log/oracledb/ touch /var/log/oracledb/oracledb.log 2. Add the following line to /etc/rsyslog.conf: local1.info /var/log/oracledb/oracledb.log 3.Configuring Logging on Network Elements Note: The […]
with t as ( select ss.run_time,ts.name,round(su.tablespace_size*dt.block_size/1024/1024/1024,2) alloc_size_gb, round(su.tablespace_usedsize*dt.block_size/1024/1024/1024,2) used_size_gb from dba_hist_tbspc_space_usage su, (select trunc(BEGIN_INTERVAL_TIME) run_time,max(snap_id) snap_id from dba_hist_snapshot group by trunc(BEGIN_INTERVAL_TIME) ) ss, v$tablespace ts, dba_tablespaces dt where su.snap_id = ss.snap_id and su.tablespace_id = ts.ts# and ts.name =upper(‘USERS’) and ts.name = dt.tablespace_name ) select e.run_time,e.name,e.alloc_size_gb,e.used_size_gb curr_used_size_gb, b.used_size_gb prev_used_size_gb, case when e.used_size_gb > b.used_size_gb then to_char(e.used_size_gb – b.used_size_gb) when e.used_size_gb = […]