A recent question on the database OTN forum and a previous request by Charles Hooper that I cover some basic indexing concepts for newbie’s who might be confused by “dubious” information out there in internet land has prompted me to discuss the BLKS_GETS_PER_ACCESS metric, available in INDEX_STATS after an analyze validate structure operation.   The OTN [...]

I always take notice when Oracle introduces a new “FAST” option, so it was with some excitement when I first noticed in Oracle 11g Rel 1 there was a new FAST option when running the ANALYZE TABLE CASCADE VALIDATE STRUCTURE command.   This was described in the manuals as introducing a hashing scheme that was significantly [...]

In my previous post, I discussed how Oracle from 11g R2 onwards will automatically drop the segment and associated storage from unusable index objects. Mohamend Houri asked in the comments section the excellent question of just how useful this feature will be in real life cases when typically indexes are not left in an unusuable state for a [...]

Following on from my previous discussion on “Create On Demand” segments, Oracle 11g R2 has also introduced storage saving initiatives in relation to useable indexes.  Starting with a simple Oracle 10g example, we create a table and associated index:        If we now make the index unusable:        We notice that [...]

Prior to Oracle11g Release 2, the default and minimum size of a segment is one extent. So in the below example, where we create a table and five associated indexes:     Each of the segments has been allocated an extent, including each of the indexes.   However, since Oracle11g Release 2, this default behaviour has changed. [...]

With each new database release, nice little improvements and enhanced options continually get added. Since 11g R1, two index related features can finally be used in combination with each other.   To demonstrate, I’m first going to create and populate a so-called “large” Data Warehouse table.      I’ll next create a standard bitmap index [...]

An interesting new hint was introduced in Oracle11g which provides an alternative approach when inserting data where duplicate values might be an issue.   To illustrate, I’m going to create a little table with just the 10 rows with a unique ID column containing values 1 – 10 policed by a Unique index:     If [...]

As I’ve been focusing mainly with Oracle 11g at work these days, thought I might look at a number of Oracle 11g related topics in the coming weeks.   To start with, there’s been a subtle but potentially significant change introduced in Oracle 11g (since 11.1.0.6) with regard to the manner in which locks are [...]

The intent of this blog piece is just to bring together the whole discussion of block dumps and how we can use block dumps to demonstrate Oracle behaviour. First, let’s start with a fresh little demo, creating an index on a NAME column with 500 entries (note this specific demo uses an 11.2.0.1 database running [...]

Finally, we look at the last portion of the index block dump which refers to the actual 3 index entries in our demo that currently reside within the index leaf block we dumped previously. row#0[8021] flag: ——, lock: 0, len=15 col 0; len 5; (5):  42 4f 57 49 45 col 1; len 6; (6):  02 01 48 8a [...]