sql*plus

Role of # in SQL*Plus

The # character is for commenting in SQL*Plus, right?

The character # has been mostly used for comments in many languages, such as shell scripts and python. Interestingly # is legal syntax in SQL scripting as well; but is it considered a comment? The answer is no; it's not. The purpose of # in SQL scripts is very different. and you should be very careful using it.

Entering # tells SQL*Plus to temporarily pauses what has been entered before and execute everything after that #sign, as if in a different session. Here is a usecase. Suppose you are writing this query:

SQL> select *
  2  from v$sesstat
  3  where

Enough with AFIEDT.BUF

You are in SQL*Plus. You entered a command and urgh, there was a typo. No worries, you bring up the command in an editor by typing:

SQL> ed

This opens up an editor, such as notepad.exe in Windows or vi in Unix, etc. And it puts the last SQL you entered in a file, oddly named, afiedt.buf. You don't like it and you want a name easier to type. Is it possible? Of course.

History of Afiedt.Buf

First a little bit of background information on the odd name. SQL*Plus as a tool evolved from another tool Oracle provided a long, long time ago, called--rather uncreatively--User Friendly Interface, or UFI. When the editor wanted to bring up a file for editing, the file had to be given a name unique enough so as not to conflict with anything else. Therefore the file was named ufiedt.buf, which roughly indicated UFI Editor Buffer.

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New Version Of XPLAN_ASH Utility

A new version 4.23 of the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

This version comes only with minor changes, see the change log below.

Here are the notes from the change log:

- Finally corrected the very old and wrong description of "wait times" in the script comments, where it was talking about "in-flight" wait events but that is not correct. ASH performs a "fix-up" of the last 255 samples or so and updates them with the time waited, so these wait events are not "in-flight"

- Removed some of the clean up code added in 4.22 to the beginning of the script, because it doesn't really help much but spooled script output always contained these error messages about non-existent column definitions being cleared

New Version Of XPLAN_ASH Utility

A new version 4.22 of the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

This version primarily addresses an issue with 12c - if the HIST mode got used to pull ASH information from AWR in 12c it turned out that Oracle forgot to add the new "DELTA_READ_MEM_BYTES" columns to DBA_HIST_ACTIVE_SESS_HISTORY - although it got officially added to V$ACTIVE_SESSION_HISTORY in 12c. So now I had to implement several additional if/then/else constructs to the script to handle this inconsistency. It's the first time that the HIST view doesn't seem to reflect all columns from the V$ view - very likely an oversight rather than by design I assume.

New Version Of XPLAN_ASH Utility - In-Memory Support

A new version 4.21 of the XPLAN_ASH utility is available for download. I publish this version because it will be used in the recent video tutorials explaining the Active Session History functionality of the script.

As usual the latest version can be downloaded here.

This is mainly a maintenance release that fixes some incompatibilities of the 4.2 version with less recent versions (10.2 and 11.2.0.1).

As an extra however, this version now differentiates between general CPU usage and in-memory CPU usage (similar to 12.1.0.2 Real-Time SQL Monitoring). This is not done in all possible sections of the output yet, but the most important ones are already covered.

Video Tutorial: XPLAN_ASH Active Session History - Introduction

I finally got around preparing another part of the XPLAN_ASH video tutorial.

This part is about the main funcationality of XPLAN_ASH: SQL statement execution analysis using Active Session History and Real-Time SQL Monitoring.

In this video tutorial I'll explain what the output of XPLAN_ASH is supposed to mean when using the Active Session History functionality of the script. Before diving into the details of the script output using sample reports I provide some overview and introduction in this part that hopefully makes it simpler to understand how the output is organized and what it is supposed to mean.

This is the initial, general introduction part. More parts to follow.

New Version Of XPLAN_ASH Utility

A new version 4.2 of the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

There were no too significant changes in this release, mainly some new sections related to I/O figures were added.

One thing to note is that some of the sections in recent releases may require a linesize larger than 700, so the script's settings have been changed to 800. If you use corresponding settings for CMD.EXE under Windows for example you might have to adjust accordingly to prevent ugly line wrapping.

Here are the notes from the change log:

- New sections "Concurrent activity I/O Summary based on ASH" and "Concurrent activity I/O Summary per Instance based on ASH" to see the I/O activity summary for concurrent activity

New Version Of XPLAN_ASH Utility

A new version 4.1 of the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

This version in particular supports now the new 12c "Adaptive" plan feature - previous versions don't cope very well with those if you don't add the "ADAPTIVE" formatting option manually.

Here are the notes from the change log:

- GV$SQL_MONITOR and GV$SQL_PLAN_MONITOR can now be customized in the
settings as table names in case you want to use your own custom monitoring repository that copies data from GV$SQL_MONITOR and GV$SQL_PLAN_MONITOR in order to keep/persist monitoring data. The tables need to have at least those columns that are used by XPLAN_ASH from the original views

New Version Of XPLAN_ASH Utility

A minor update 4.01 to the XPLAN_ASH utility is available for download.

As usual the latest version can be downloaded here.

These are the notes from the change log:

- More info for RAC Cross Instance Parallel Execution: Many sections now show a GLOBAL aggregate info in addition to instance-specific data

- The Parallel Execution Server Set detection and ASSUMED_DEGREE info now makes use of the undocumented PX_STEP_ID and PX_STEPS_ARG info (bit mask part of the PX_FLAGS column) on 11.2.0.2+

- Since version 4.0 added from 11.2.0.2 on the PX *MAX* DOP in the "SQL statement execution ASH Summary" based on the new PX_FLAGS column of ASH it makes sense to add a PX *MIN* DOP in the summary to see at one glance if different DOPs were used or not