MADHAN APPS DBA

 How INSERT Statement Works in Oracle: 1.When Oracle receives sql/insert query,it requires to run some pre-tasks before actually being able to really run the query. 2.During parsing,Database validate the syntax of the statement whether the query is valid or not. 3.Database validate the semantic of the statement.It checks whether a statement is meaningful or not. 4.If syntax/Semantic check pass,then server process will continue execution of the query. The server process will go to the library cache.In the library cache the server process will search from the MRU (Most Recently Used) end to the LRU (Least Recently Used) end for a match for the sql statement. It does this by using a hash algorithm that returns a hash value.If the hash value of the query we have written matches with that of the query in library cache then server process need not generate an execution plan (soft parsing) but if no match is found then server process has to proceed with the generation of execution plan (h...

 In the PREPARE phase, ADOP does a series of validations and then “prepares” the system for an online patching cycle. Here is a rundown of what happens step-by-step when we run adop phase=prepare First, it preforms the verification of parameters and checks for various minor pre-reeqs Performing verification of parameters Sourcing the Run Edition environment Validating system setup… Determining admin node Node registry is valid. Performing database sanity checks Acquire lock on sessions table Checking for pending adop sessions active hotpatch session… active cleanup session active FS_CLONE session Staging new adop session… Checking if node “<node_name>” previously failed New row inserted into ad_adop_sessions table with session id : 100 Unlocking sessions table createPatchCtxFile() check if patch context file exists, else generate it (from where?) Checking the status of phase select  count(1)   from  ad_adop_sessions  where  adop_session_id=100   ...

 adcfgclone on database node we had three modes in which it can be executed.   1)perl adcfgclone.pl dbTier:    It will configure the ORACLE_HOME on the target database tier node and  recreate the controlfiles.  This is specially used in case of standby database and/or hot backups. It will take care of all the steps.    2)perl adcfgclone.pl dbTechStack   It will configure the ORACLE_HOME on the target database tier node only. Relink the oracle home.   The below steps has to be performed manually 1. Create the Target Database control files. 2. Start the Target System Database in open mode 3. Run the library update script against the Database cd $RDBMS_ORACLE_HOME/appsutil/install/[CONTEXT NAME] sqlplus "/ as sysdba" @adupdlib.sql [libext]  Where [libext] should be set to 'sl' for HP-UX, 'so' for any other UNIX platform, or 'dll' for Windows.   3)perl adcfgclone.pl dbconfig   It is used to configure the database with  co...

 Types of Standby Databases: ======================= Physical Standby Logical Standby Snapshot Standby Active data guard 1.PHYSICAL STANDBY: 1.Physical Standby is the exact block-for-block copy of the primary database. 2.Physical standby database synchronized with the primary database through the application of redo data received from the primary database. 3.It can be used concurrently for data protection and reporting.    4.Physical standby database will be mounted stage while recovery is processed. 5.It can be opened as read-only mode 6.Active standby database is available for reading mode, enabling recovery at the backend.  Physical standby database benefits: 1.An identical physical copy of the primary database. 2.Disaster recovery and high availability. 3.High Data protection. 4.Reduction in primary database workload. 5.Performance can be Faster. 2.LOGICAL STANDBY: 1.A logical standby database does not have to match the schema structure of the source database. 2....

 ERROR: Concurrent program error-ed out with below error, Failed to write core dump. Core dumps have been disabled. To enable core dumping, try “ulimit -c unlimited” before starting Java again SOLUTION: Before: --------- [root@ ~]# ulimit -c -l core file size (blocks, -c) 0 max locked memory (kbytes, -l) 64 Here ulimit core file size is 0 so change it to unlimited. After: -------- [root@ ~]# ulimit -c unlimited [root@~]# ulimit -c -l core file size (blocks, -c) unlimited max locked memory (kbytes, -l) 64