SQL*Net Wires Crossed

I was trying to set up Data Guard between two servers and I kept getting connection errors from RMAN on the primary to the secondary:
RMAN>  connect auxiliary sys/syspassword@dgtest_stdby

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-04006: error from auxiliary database: ORA-01017: invalid username/password; logon denied

All Outer Joins Are Not Equal

When executing SQL involving ANSI syntax OUTER JOIN's Oracle first converts this to its own native syntax before executing the SQL, and sometimes this conversion is not totally transparent thereby affecting and restricting the execution plan produced.

This started when I had a long running query, and it happened to (more...)

NULLs & Multi-Column Indexes

Previously I showed some of the issues with allowing NULL values in columns and how indexes might be ignored by the Optimizer. All of the examples I gave involved single column indexes only, and showed that NULL values are not stored in such an index. As others have pointed out (more...)

NULLs and Indexes

It is quite clear that Oracle does not store NULL values within indexes (B-Tree indexes specifically, being the most common type used within Oracle). This has been the case for many years - I remember reading about this in the version 7 days over 15 years ago. My understanding was (more...)

Avoiding NULLs

On the one hand I understand the added value of the concept of a "NULL" value - meaning that no value has been stored in a column in a row in a database table. On the other hand I have always felt that allowing NULL values in a column leads (more...)