Oracle DBACategory

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… Continue Reading Clustering Factor and it’s effect on non-assm and assm tablespace

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… Continue Reading Index in 12c by example test case

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… Continue Reading Index internal oracle using simple test case

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… Continue Reading How histogram can affect query plan change hence performance

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… Continue Reading Poor index identify and resolve manually or using sql tuning advisor

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… Continue Reading Installation of Oracle 12c RAC Flex cluster infrastructure on Virtual Box

  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… Continue Reading EXPDP and IMPDP command reference 12c

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… Continue Reading Oracle Database Audit FGA using SYSLOG to capture

This document will help you providing guideline to upgrade Oracle 11g RAC to Oracle 12c RAC clusterware  and Database . Author:-Saibal Ghosh https://www.linkedin.com/in/saibal-ghosh-ccsk-prince2-%C2%AE-469b0a7/ 1 Tasks Before Upgrade 1.1 Backup the Database: Before we start the upgrade, it is a best practice to backup the database, Oracle Cluster Registry (OCR) and… Continue Reading Upgrade of Oracle 11g RAC database to Oracle 12c RAC DBUA

Error in dataguard alert log/start managed recovery process:- SYS@XXX>alter database recover managed standby database; alter database recover managed standby database * ERROR at line 1: ORA-00283: recovery session canceled due to errors ORA-01111: name for data file 61 is unknown – rename to correct file ORA-01110: data file 61: ‘/u01/app/oracle/product/12.1.0/db_1/dbs/UNNAMED00061’… Continue Reading ORA-01111: name for data file is unknown – rename to correct file