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Index Fast Full Scan

Index Fast Full Scan is one of the index access methods supported by Oracle. Index Fast Full Scan is otherwise called as Fast Full Index Scan also. Index Fast Full Scan can be imposed by Oracle Optimizer only in the certain scenario. The scenario where this index would be invoked is, Whenever the Oracle SQL optimizer detects that the query is serviceable without touching table rows, Oracle invokes this fast full index scan and quickly reads every block of the index without touching the table itself provided that query doesn’t contain any ORDER BY clause. The definition for this scan is more or less similar to the index full scan but the only difference is that former will be invoked when ORDER BY clause is not mentioned in the query. It differs from the index full scan in another way where output won’t be in the sorted order since ORDER BY clause is not mentioned. If Oracle detects the query is serviceable without touching the table rows, it means, all the columns mentioned i...

Listener refused the connection due to NetException

I was testing some piece of code for calculation of new date on the basis of a given pattern and the specified date. I wrote a method to automate the test cases to generates those patterns and calculate the new date for each date of the specified date of the range of years. Since there were around 1 million pattern test cases are possible, so I want to insert this data in database for any future reference. After creating a pattern I was inserting data of the pattern and the calculation date along with the calculated date. It was working fine. I was prepare to hit the start button now, after testing different patterns individually. I hit the run button and it started its executions, but in the middle, I got this error. java.sql.SQLException: Listener refused the connection with the following error:ORA-12516, TNS:listener could not find available handler with matching protocol stack at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:4...

Bitmap index

Bitmap index is one of the index types that is supported by oracle. Unlike B*tree index, this is very compressed index. It means if I create a bitmap index on a column, then the generated index table will be smaller when compared the index table which is generated by the binary index on the same column. The reason is, in bitmap index, ROWIDs won’t be stored in the index table, instead index values will be mapped against bitmaps. Bitmap is nothing but it stores either of this values, 1(Match) or 0(No Match). For each distinct values in the column, a separate index record will be created. Unlike b*tree index, bitmap index can accept NULL and it creates separate index entry for this. Bitmap index will work better if number of distinct values are relatively less when compared to the total number of records. Why is it referred as “relatively less”? this index will work fine if table of 1,000,000,000 records contains 5000 distinct values and if table of 1,000 records contains 5 distinct va...

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