Analysis Challenges

April 25, 2013

Roughly 12 years ago I was attempting to analyze customer order changes that were received through electronic document interchange (EDI), specifically X12 830 documents that show order forecasted demand for specific part numbers.  At the time, the EDI data was partially transformed and inserted into an Oracle 8.0.5 database, while that data is now inserted into an Oracle 11.2 database.  I recently took another glance that this particular problem to see if there is a better method for performing the analysis.

Complications in the analysis:

• The EDI documents do not include the customer’s purchase order line numbers, just a list of outstanding due dates and quantities.  That complication means that there is no easy way to see if an outstanding quantity has changed, or the date for that outstanding quantity has changed.
• It is possible to ship to the customer a partial order quantity, with the remaining quantity on the line handled as a back-order.  If the customer does not alter this particular forecast line, only the quantity outstanding will be provided, along with the due date – the original quantity is not provided.
• It is possible to ship out an order line received in an 830 document up to five days before the customer’s due date.
• Shipped parts may require hours or days to reach the customer’s site, thus delaying when those shipped parts are acknowledged in the list of outstanding due dates and quantities received through EDI.
• EDI 830 documents are generally received the next weekday after the customer batch generates those documents on a nightly basis.  Thus, there is an opportunity for the received forecast to be out of sync with what is known to have arrived at the customer site, and what is acknowledged in the EDI data.
• The customer may generate multiple EDI 830 documents for a particular part number/purchase order combination on any given day, and only the EDI 830 document received with the highest (sorted in ascending order) release number (which may not be a number) on a specific date is the valid release for the specific date.
• EDI 830 documents may be generated for a specific part number by the customer nearly every weekday, once a month, or any frequency in between.

I recall trying to find a solution to this particular problem 12 years ago.  I thought that I could possibly pull all of the relevant data from the Oracle database into a custom application, and through some magical formula output what appeared to be a list of what the customer changed.  However, what about those part quantities that are in transit to the customer?  What about those part quantities that were received by the customer, but had not yet made their way through the customer’s batch processing system?  What about those cases where the customer sents two or more EDI 830 releases for a specific part number, and those EDI releases are received on the same date?

At the time, I was frustrated.  The quality of the output of my analysis would be dependent on the accuracy of humans (yes, and humans wrote the program that performed the analysis too).  I simply had to find the first matching due date and order quantity from the previous release with the due date and order quanitity from the current release, and then rely on an end user to correct the 5% to 10% of the cases where the matching algorithm was wrong due to one or more of the “complications” outlined above.

—

While recently re-examining the problem, I noticed a data element in the EDI 830 document that is described as “ACCUM RECEIPTS AS OF THIS DATE”, and a luck would have it, that particular data element is one of those elements that was selected more than 12 years ago to be transformed into the Oracle Database tables (in the sample data included with this blog article, this column is named PREVIOUS_ACCUM_QTY).  If only I recognized the meaning of the values of this column, and had access to Oracle analytical SQL functions 12 years ago, this particular analysis problem might not have had so many variables that could potentially throw off the quality of the analysis.

This particular blog article has a fairly large set of sample data – however, that sample data is a fairly small subset of the data that must be analyzed on a daily basis.  The sample data may be downloaded here: analysischallenges.sql sample code (save the file as “analysischallenges.sql” – without the .doc double extension).  If the file is saved in the same directory (folder) as SQL*Plus was started from, you may then execute the script in SQL*Plus to build the tables and populate the sample data by using the following command:

@analysischallenges.sql

The two sample table definitions are created with the following commands (also included in the script):

CREATE TABLE T1 (
  CUSTOMER_PO VARCHAR2(15),
  RELEASE_ID VARCHAR2(15),
  PART_ID VARCHAR2(30),
  RELEASE_DATE DATE,
  PREVIOUS_ACCUM_QTY NUMBER,
  CREATE_DATE DATE,
  PRIMARY KEY (CUSTOMER_PO,RELEASE_ID));

CREATE TABLE T1_LINE (
  CUSTOMER_PO VARCHAR2(12),
  RELEASE_ID VARCHAR2(12),
  QTY NUMBER,
  DUE_DATE DATE,
  PRIMARY KEY (CUSTOMER_PO,RELEASE_ID,DUE_DATE));

T1 Table Columns:

CUSTOMER_PO is the unique identifier for the customer purchase order received through the EDI 830 documents.  RELEASE_ID defines the specific serialized change number for the customer’s PO – the RELEASE_ID is unique for a specific PO.  PART_ID is the part number for which the customer is providing a forecast.  RELEASE_DATE is the date that the forecast was batch generated in the customer’s computer system.  PREVIOUS_ACCUM_QTY is the count of the number of this part number that the customer has already received for this specific customer purchase order.  CREATE_DATE is the date that the forecast was received from the customer and transformed/inserted into the Oracle Database tables.

T1_LINE Table Columns:

CUSTOMER_PO and RELEASE_ID are undeclared foreign key columns that point back to table T1.  QTY is the quantity of the part number that should (or is forecasted to) ship on the specfied DUE_DATE.

—–

If you are curious how I created the script to populate the tables, I executed the following in SQL*Plus, and then performed a little cleanup of the resulting spool files:

SET LINESIZE 200
SET TRIMSPOOL ON

SPOOL analysischallenges_t1.txt

SELECT
  'INSERT INTO T1 VALUES ('||CHR(39)||CUSTOMER_PO||CHR(39)||','
    ||CHR(39)||RELEASE_ID||CHR(39)||','
    ||CHR(39)||PART_ID||CHR(39)||','
    ||'TO_DATE('||CHR(39)||TO_CHAR(RELEASE_DATE,'DD-MON-YYYY')||CHR(39)||','||CHR(39)||'DD-MON-YYYY'||CHR(39)||')'||','
    ||PREVIOUS_ACCUM_QTY||','
    ||'TO_DATE('||CHR(39)||TO_CHAR(CREATE_DATE,'DD-MON-YYYY')||CHR(39)||','||CHR(39)||'DD-MON-YYYY'||CHR(39)||')'||');' D
FROM
  T1
ORDER BY
  CUSTOMER_PO,
  RELEASE_ID;

SPOOL OFF

SPOOL analysischallenges_t1_line.txt

SELECT
  'INSERT INTO T1_LINE VALUES ('||CHR(39)||CUSTOMER_PO||CHR(39)||','
    ||CHR(39)||RELEASE_ID||CHR(39)||','
    ||QTY||','
    ||'TO_DATE('||CHR(39)||TO_CHAR(DUE_DATE,'DD-MON-YYYY')||CHR(39)||','||CHR(39)||'DD-MON-YYYY'||CHR(39)||')'||');' D
FROM
  T1_LINE
ORDER BY
  CUSTOMER_PO,
  RELEASE_ID,
  DUE_DATE;

SPOOL OFF

—–

We must find a starting point for performing the analysis of what changed from one day’s forecast to a prior day’s forecast.  There is an issue with the EDI 830 releases that were received (identified by the CREATE_DATE column) on April 24, 2013 – two releases for the same customer purchase orders were received, and there were two purchase orders that demand the same part number.  Our analysis is only concerned with the highest numbered (sorted alphabetically) release number document for each customer purchase order that was received on any particular day, so we need to find a way to eliminate the other older releases for the same customer purchase order that was received on the same day.  The ROW_NUMBER analytic function is perfect for this task – we just need the output to show the same number (1) for the rows that we want to keep, and have some other number appear on the other rows.  Something similar to the following may work (note that the TRUNC function, or other approach that uses a date/time range, probably should be used when working with the CREATE_DATE column – realistically, there could be a time component included with those date values):

COLUMN PART_ID FORMAT A10
SET LINESIZE 120
SET PAGESIZE 1000

SELECT
  T.PART_ID,
  T.CUSTOMER_PO,
  ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
  T.RELEASE_ID,
  T.RELEASE_DATE,
  T.CREATE_DATE,
  T.PREVIOUS_ACCUM_QTY
FROM
  T1 T
WHERE 
  T.CREATE_DATE=TO_DATE('24-APR-2013','DD-MON-YYYY')
ORDER BY
  T.PART_ID,
  T.CUSTOMER_PO,
  T.RELEASE_ID;

PART_ID    CUSTOMER_PO     REL_ON_DATE RELEASE_ID      RELEASE_D CREATE_DA PREVIOUS_ACCUM_QTY
---------- --------------- ----------- --------------- --------- --------- ------------------
DS1812+    1231234                   2 20130402-001    23-APR-13 24-APR-13                 24
DS1812+    1231234                   1 20130403-001    24-APR-13 24-APR-13                 24
DS1812+    1233290                   2 20130402-001    23-APR-13 24-APR-13                  4
DS1812+    1233290                   1 20130403-001    24-APR-13 24-APR-13                  4
DS212+     1133290                   2 20130402-001    23-APR-13 24-APR-13                  2
DS212+     1133290                   1 20130403-001    24-APR-13 24-APR-13                  2
RS812      1231280                   2 20130402-001    23-APR-13 24-APR-13                 60
RS812      1231280                   1 20130403-001    24-APR-13 24-APR-13                 60

To remove all of the rows that have something other than 1 in the REL_ON_DATE column, we are able to slide the above SQL statement into an inline view, and then specify that the REL_ON_DATE column value must be equal to 1.  Typically, there are supposed to be few/no changes made by the customer within eight weeks of the customer forecast’s release date, but that is not always the case.  While eliminating the unnecessary releases, it probably makes sense to also calculate the end date of this “firm” period by adding 55 days to the date on which the forecast was created:

SELECT
  T.PART_ID,
  T.CUSTOMER_PO,
  T.RELEASE_ID,
  T.RELEASE_DATE+55 POSSIBLE_FIRM_DATE,
  T.PREVIOUS_ACCUM_QTY
FROM
  (SELECT
    T.PART_ID,
    T.CUSTOMER_PO,
    ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
    T.RELEASE_ID,
    T.RELEASE_DATE,
    T.CREATE_DATE,
    T.PREVIOUS_ACCUM_QTY
  FROM
    T1 T
  WHERE 
    T.CREATE_DATE=TO_DATE('24-APR-2013','DD-MON-YYYY')) T
WHERE
  T.REL_ON_DATE=1
ORDER BY
  T.PART_ID,
  T.CUSTOMER_PO,
  T.RELEASE_ID;

PART_ID    CUSTOMER_PO     RELEASE_ID      POSSIBLE_ PREVIOUS_ACCUM_QTY
---------- --------------- --------------- --------- ------------------
DS1812+    1231234         20130403-001    18-JUN-13                 24
DS1812+    1233290         20130403-001    18-JUN-13                  4
DS212+     1133290         20130403-001    18-JUN-13                  2
RS812      1231280         20130403-001    18-JUN-13                 60

Next, we need to retrieve the forecasted delivery schedule (in the T1_LINES table) that are associated with the above rows.  If we take the value in the PREVIOUS_ACCUM_QTY column, and find a way to generate a running SUM of the QTY column from the T1_LINE table, in theory we should be able to determine if the total quantity ordered through a specific date has changed.  The analytic version of the SUM function offers the capability of producing a running SUM when an ORDER BY clause is included in the function call.  To reduce the data set size, I will only consider those forecasts with a scheduled delivery date that is within 101 days of the customer’s forecast date.  With those changes in place, the SQL statement is modified as follows:

SELECT
  T.PART_ID,
  T.CUSTOMER_PO,
  T.RELEASE_ID,
  T.RELEASE_DATE+55 POSSIBLE_FIRM_DATE,
  T.PREVIOUS_ACCUM_QTY,
  TL.DUE_DATE,
  TL.QTY,
  T.PREVIOUS_ACCUM_QTY + SUM(TL.QTY) OVER (PARTITION BY T.CUSTOMER_PO,T.RELEASE_ID ORDER BY TL.DUE_DATE) REL_RUNNING_SUM
FROM
  (SELECT
    T.PART_ID,
    T.CUSTOMER_PO,
    ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
    T.RELEASE_ID,
    T.RELEASE_DATE,
    T.CREATE_DATE,
    T.PREVIOUS_ACCUM_QTY
  FROM
    T1 T
  WHERE 
    T.CREATE_DATE=TO_DATE('24-APR-2013','DD-MON-YYYY')) T,
  T1_LINE TL
WHERE
  T.REL_ON_DATE=1
  AND T.CUSTOMER_PO=TL.CUSTOMER_PO
  AND T.RELEASE_ID=TL.RELEASE_ID
  AND (T.RELEASE_DATE+100)>=TL.DUE_DATE
ORDER BY
  T.PART_ID,
  T.CUSTOMER_PO,
  T.RELEASE_ID,
  TL.DUE_DATE;

PART_ID    CUSTOMER_PO     RELEASE_ID      POSSIBLE_ PREVIOUS_ACCUM_QTY DUE_DATE         QTY REL_RUNNING_SUM
---------- --------------- --------------- --------- ------------------ --------- ---------- ---------------
DS1812+    1231234         20130403-001    18-JUN-13                 24 24-APR-13          0              24
DS1812+    1233290         20130403-001    18-JUN-13                  4 24-APR-13          0               4
DS212+     1133290         20130403-001    18-JUN-13                  2 24-APR-13          0               2
RS812      1231280         20130403-001    18-JUN-13                 60 27-JUN-13          1              61
RS812      1231280         20130403-001    18-JUN-13                 60 03-JUL-13          1              62
RS812      1231280         20130403-001    18-JUN-13                 60 24-JUL-13          2              64

As may be seen above, only customer purchase order 1231280 has a forecast, calling for a quantity of 1 on June 27, quantity of 1 on July 3, and a quantity of 2 on July 24.  The previously received quantity for customer purchase order 1231280 is 60, so the additional forecast quantities will bring the total order quantities up to 61, 62, and 64 through the three dates included in the forecast.

-The Top Half of the Final SQL Statement is Above-

–

So, we now have a starting point – the data that was received on April 24, 2013.  How does that forecast data compare with previously received forecasts?  We need to start building the second half of the SQL statement, which looks at the historical data.  To limit the dataset size, I will limit the data to only those EDI documents that were received up to 56 days prior (the eight week “firm” period) to the April 24, 2013 date that was specified earlier in this article:

SELECT
  T.CUSTOMER_PO,
  ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
  TRUNC(T.CREATE_DATE) CREATE_DATE,
  T.RELEASE_ID,
  T.PREVIOUS_ACCUM_QTY
FROM
  T1 T
WHERE 
  T.CREATE_DATE >= TO_DATE('24-APR-2013','DD-MON-YYYY') - 56
  AND T.CREATE_DATE < TO_DATE('24-APR-2013','DD-MON-YYYY')
ORDER BY
  T.CUSTOMER_PO,
  T.RELEASE_ID;

CUSTOMER_PO     REL_ON_DATE CREATE_DA RELEASE_ID      PREVIOUS_ACCUM_QTY
--------------- ----------- --------- --------------- ------------------
1131111                   1 27-FEB-13 0371                           575
1131111                   1 01-MAR-13 0381                           577
1131111                   1 06-MAR-13 0431                           578
1131111                   1 07-MAR-13 0441                           581
1131111                   1 08-MAR-13 0451                           581
1131111                   1 11-MAR-13 0461                           581
...
1131111                   1 08-APR-13 0741                           593
1131111                   1 11-APR-13 0791                           593
1131111                   1 23-APR-13 0911                           595
1131245                   1 27-FEB-13 0371                          2299
1131245                   1 01-MAR-13 0381                          2300
1131245                   1 05-MAR-13 0421                          2303
...
1131745                   1 19-APR-13 0871                           435
1131745                   1 23-APR-13 0911                           435
1133290                   1 27-FEB-13 20130205-001                     2
1133290                   1 28-FEB-13 20130206-001                     2
1133290                   1 01-MAR-13 20130207-001                     2
...
1133290                   1 19-APR-13 20130328-001                     2
1133290                   1 23-APR-13 20130401-001                     2
1231234                   1 27-FEB-13 20130205-001                    24
1231234                   1 28-FEB-13 20130206-001                    24
...
1231234                   1 23-APR-13 20130401-001                    24
1231280                   1 27-FEB-13 20130205-001                    57
1231280                   1 28-FEB-13 20130206-001                    57
1231280                   1 01-MAR-13 20130207-001                    57
1231280                   1 04-MAR-13 20130208-001                    58
1231280                   1 05-MAR-13 20130211-001                    58
...
1231280                   1 04-APR-13 20130313-001                    60
1231280                   2 05-APR-13 20130314-002                    60
...
1231280                   1 19-APR-13 20130328-001                    60
1231280                   1 23-APR-13 20130401-001                    60
1233290                   1 27-FEB-13 20130205-001                     4
1233290                   1 28-FEB-13 20130206-001                     4
...

As we found earlier, there could be more than one release for a customer purchase order received in a single date, and we are only concerned with the most recent release received on any particular day.  We have a second issue, in that the dates may have shifted from one release to the next, so we have to artifically generate rows with the potentially missing dates, with an order quantity of 0 on those dates.

But, how to generate a list of dates?  We could use a CONNECT BY LEVEL trick:

SELECT
  TO_DATE('24-APR-2013','DD-MON-YYYY')+(LEVEL-1) DUE_DATE
FROM
  DUAL
CONNECT BY
  LEVEL<=100;

DUE_DATE
---------
24-APR-13
25-APR-13
26-APR-13
27-APR-13
28-APR-13
...
15-JUN-13
16-JUN-13
17-JUN-13
18-JUN-13
...
30-JUL-13
31-JUL-13
01-AUG-13

Now, by creating a Cartesian join between the dataset with the dates and the dataset with the EDI release header records, we will make certain that a date exists for every date that is potentially of interest (up to 100 days after April 24, 2013) when we later join the result with the T1_LINE table (the child table that lists the forecast delivery dates).

SELECT
  T2.CUSTOMER_PO,
  T2.RELEASE_ID,
  T2.CREATE_DATE,
  T2.PREVIOUS_ACCUM_QTY,
  D.DUE_DATE
FROM
  (SELECT
    T.CUSTOMER_PO,
    ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
    TRUNC(T.CREATE_DATE) CREATE_DATE,
    T.RELEASE_ID,
    T.PREVIOUS_ACCUM_QTY
  FROM
    T1 T
  WHERE 
    T.CREATE_DATE >= TO_DATE('24-APR-2013','DD-MON-YYYY') - 56
    AND T.CREATE_DATE < TO_DATE('24-APR-2013','DD-MON-YYYY')
  ORDER BY
    T.CUSTOMER_PO,
    T.RELEASE_ID) T2,
  (SELECT
    TO_DATE('24-APR-2013','DD-MON-YYYY')+(LEVEL-1) DUE_DATE
  FROM
    DUAL
  CONNECT BY
    LEVEL<=100) D
WHERE
  T2.REL_ON_DATE=1
ORDER BY
  T2.CUSTOMER_PO,
  T2.RELEASE_ID,
  D.DUE_DATE;

...
CUSTOMER_PO     RELEASE_ID      CREATE_DA PREVIOUS_ACCUM_QTY DUE_DATE
--------------- --------------- --------- ------------------ ---------
1233290         20130318-001    09-APR-13                  4 25-MAY-13
1233290         20130318-001    09-APR-13                  4 26-MAY-13
1233290         20130318-001    09-APR-13                  4 27-MAY-13
1233290         20130318-001    09-APR-13                  4 28-MAY-13
...
1233290         20130322-001    15-APR-13                  4 22-JUN-13
1233290         20130322-001    15-APR-13                  4 23-JUN-13
1233290         20130322-001    15-APR-13                  4 24-JUN-13
1233290         20130322-001    15-APR-13                  4 25-JUN-13
...
1233290         20130401-001    23-APR-13                  4 29-JUL-13
1233290         20130401-001    23-APR-13                  4 30-JUL-13
1233290         20130401-001    23-APR-13                  4 31-JUL-13
1233290         20130401-001    23-APR-13                  4 01-AUG-13

Next, we will outer join to the T1_LINE table to bring in the actual forecasted delivery schedule from the previous dates (note that I also removed an unnecessary ORDER BY clause that was still embedded in the SQL statement – the Oracle query optimizer probably would have realized that the ORDER BY clause was meaningless to the query result, and automatically removed it – but I removed the clause just in case my assumption is incorrect):

SELECT
  T3.CUSTOMER_PO,
  T3.CREATE_DATE,
  T3.DUE_DATE,
  T3.PREVIOUS_ACCUM_QTY + SUM(NVL(TL.QTY,0)) OVER (PARTITION BY T3.CUSTOMER_PO,T3.RELEASE_ID ORDER BY T3.DUE_DATE) REL_RUNNING_SUM
FROM
  (SELECT
    T2.CUSTOMER_PO,
    T2.RELEASE_ID,
    T2.CREATE_DATE,
    T2.PREVIOUS_ACCUM_QTY,
    D.DUE_DATE
  FROM
    (SELECT
      T.CUSTOMER_PO,
      ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
      TRUNC(T.CREATE_DATE) CREATE_DATE,
      T.RELEASE_ID,
      T.PREVIOUS_ACCUM_QTY
    FROM
      T1 T
    WHERE 
      T.CREATE_DATE >= TO_DATE('24-APR-2013','DD-MON-YYYY') - 56
      AND T.CREATE_DATE < TO_DATE('24-APR-2013','DD-MON-YYYY')) T2,
    (SELECT
      TO_DATE('24-APR-2013','DD-MON-YYYY')+(LEVEL-1) DUE_DATE
    FROM
      DUAL
    CONNECT BY
      LEVEL<=100) D
  WHERE
    T2.REL_ON_DATE=1) T3,
  T1_LINE TL
WHERE
  T3.CUSTOMER_PO=TL.CUSTOMER_PO(+)
  AND T3.RELEASE_ID=TL.RELEASE_ID(+)
  AND T3.DUE_DATE=TL.DUE_DATE(+)
ORDER BY
  T3.CUSTOMER_PO,
  T3.RELEASE_ID,
  T3.DUE_DATE;

CUSTOMER_PO     CREATE_DA DUE_DATE  REL_RUNNING_SUM
--------------- --------- --------- ---------------
1131111         27-FEB-13 24-APR-13             577
1131111         27-FEB-13 25-APR-13             578
1131111         27-FEB-13 26-APR-13             579
1131111         27-FEB-13 27-APR-13             579
1131111         27-FEB-13 28-APR-13             579
1131111         27-FEB-13 29-APR-13             580
1131111         27-FEB-13 30-APR-13             581
...
1131111         23-APR-13 30-JUL-13             636
1131111         23-APR-13 31-JUL-13             638
1131111         23-APR-13 01-AUG-13             639
...
1231280         11-MAR-13 08-MAY-13              58
1231280         11-MAR-13 09-MAY-13              58
1231280         11-MAR-13 10-MAY-13              58
1231280         11-MAR-13 11-MAY-13              58
...
1231280         23-APR-13 21-JUL-13              62
1231280         23-APR-13 22-JUL-13              62
1231280         23-APR-13 23-JUL-13              62
1231280         23-APR-13 24-JUL-13              64
1231280         23-APR-13 25-JUL-13              64
1231280         23-APR-13 26-JUL-13              64
...

We are getting close.  Now we just need to join the SQL created earlier in this article with the above SQL statement so that the current customer purchase order forecasts may be compared with the earlier received customer purchase order forecasts.  The LISTAGG analytic funtion, introduced with Oracle Database 11.1, makes it easy to condense multiple rows from the resultset into a much smaller number of rows, if the resultset is grouped on at least one column.  So, the final version of the analysis challenge appears as follows:

SELECT
  C.PART_ID,
  C.CUSTOMER_PO,
  C.POSSIBLE_FIRM_DATE,
  C.DUE_DATE,
  C.QTY,
  C.REL_RUNNING_SUM,
  LISTAGG(T4.REL_RUNNING_SUM||' ('||TO_CHAR(T4.CREATE_DATE,'MM/DD/YY')||')',', ') WITHIN GROUP (ORDER BY T4.CREATE_DATE DESC) EXCEPTIONS
FROM
  (SELECT
    T.PART_ID,
    T.CUSTOMER_PO,
    T.RELEASE_ID,
    T.RELEASE_DATE+55 POSSIBLE_FIRM_DATE,
    T.PREVIOUS_ACCUM_QTY,
    TL.DUE_DATE,
    TL.QTY,
    T.PREVIOUS_ACCUM_QTY + SUM(TL.QTY) OVER (PARTITION BY T.CUSTOMER_PO,T.RELEASE_ID ORDER BY TL.DUE_DATE) REL_RUNNING_SUM
  FROM
    (SELECT
      T.PART_ID,
      T.CUSTOMER_PO,
      ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
      T.RELEASE_ID,
      T.RELEASE_DATE,
      T.CREATE_DATE,
      T.PREVIOUS_ACCUM_QTY
    FROM
      T1 T
    WHERE 
      T.CREATE_DATE=TO_DATE('24-APR-2013','DD-MON-YYYY')) T,
    T1_LINE TL
  WHERE
    T.REL_ON_DATE=1
    AND T.CUSTOMER_PO=TL.CUSTOMER_PO
    AND T.RELEASE_ID=TL.RELEASE_ID
    AND (T.RELEASE_DATE+100)>=TL.DUE_DATE) C,
  (SELECT
    T3.CUSTOMER_PO,
    T3.CREATE_DATE,
    T3.DUE_DATE,
    T3.PREVIOUS_ACCUM_QTY + SUM(NVL(TL.QTY,0)) OVER (PARTITION BY T3.CUSTOMER_PO,T3.RELEASE_ID ORDER BY T3.DUE_DATE) REL_RUNNING_SUM
  FROM
    (SELECT
      T2.CUSTOMER_PO,
      T2.RELEASE_ID,
      T2.CREATE_DATE,
      T2.PREVIOUS_ACCUM_QTY,
      D.DUE_DATE
    FROM
      (SELECT
        T.CUSTOMER_PO,
        ROW_NUMBER() OVER (PARTITION BY T.CUSTOMER_PO,TRUNC(T.CREATE_DATE) ORDER BY T.RELEASE_ID DESC) REL_ON_DATE,
        TRUNC(T.CREATE_DATE) CREATE_DATE,
        T.RELEASE_ID,
        T.PREVIOUS_ACCUM_QTY
      FROM
        T1 T
      WHERE 
        T.CREATE_DATE >= TO_DATE('24-APR-2013','DD-MON-YYYY') - 56
        AND T.CREATE_DATE < TO_DATE('24-APR-2013','DD-MON-YYYY')) T2,
      (SELECT
        TO_DATE('24-APR-2013','DD-MON-YYYY')+(LEVEL-1) DUE_DATE
      FROM
        DUAL
      CONNECT BY
        LEVEL<=100) D
    WHERE
      T2.REL_ON_DATE=1) T3,
    T1_LINE TL
  WHERE
    T3.CUSTOMER_PO=TL.CUSTOMER_PO(+)
    AND T3.RELEASE_ID=TL.RELEASE_ID(+)
    AND T3.DUE_DATE=TL.DUE_DATE(+)) T4
WHERE
  C.CUSTOMER_PO=T4.CUSTOMER_PO
  AND C.DUE_DATE=T4.DUE_DATE
  AND C.REL_RUNNING_SUM<>T4.REL_RUNNING_SUM
GROUP BY
  C.PART_ID,
  C.CUSTOMER_PO,
  C.POSSIBLE_FIRM_DATE,
  C.DUE_DATE,
  C.QTY,
  C.REL_RUNNING_SUM
ORDER BY
  C.PART_ID,
  C.CUSTOMER_PO,
  C.DUE_DATE;

PART_ID    CUSTOMER_PO     POSSIBLE_ DUE_DATE         QTY REL_RUNNING_SUM
---------- --------------- --------- --------- ---------- ---------------
EXCEPTIONS
-----------------------------------------------------------------------------------------------------------------------
RS812      1231280         18-JUN-13 27-JUN-13          1              61
60 (03/22/13), 60 (03/21/13), 60 (03/19/13), 60 (03/18/13), 60 (03/15/13), 60 (03/14/13), 59 (03/13/13), 59 (03/12/13),
59 (03/11/13), 59 (03/08/13), 60 (03/07/13), 60 (03/06/13), 60 (03/05/13), 60 (03/04/13), 59 (03/01/13), 59 (02/28/13),
59 (02/27/13)

RS812      1231280         18-JUN-13 03-JUL-13          1              62
61 (03/22/13), 61 (03/21/13), 61 (03/19/13), 61 (03/18/13), 61 (03/15/13), 61 (03/14/13), 60 (03/13/13), 60 (03/12/13),
60 (03/11/13), 60 (03/08/13), 61 (03/07/13), 61 (03/06/13), 61 (03/05/13), 61 (03/04/13), 60 (03/01/13), 60 (02/28/13),
60 (02/27/13)

RS812      1231280         18-JUN-13 24-JUL-13          2              64
63 (03/26/13), 63 (03/25/13), 62 (03/22/13), 62 (03/21/13), 62 (03/19/13), 62 (03/18/13), 62 (03/15/13), 62 (03/14/13),
61 (03/13/13), 61 (03/12/13), 61 (03/11/13), 61 (03/08/13), 62 (03/07/13), 62 (03/06/13), 62 (03/05/13), 62 (03/04/13),
61 (03/01/13), 61 (02/28/13), 61 (02/27/13)

It is now easy to see that the requested total quantity due through June 27, 2013 increased by 2 since the first forecast which was received on February 27, 2013.  The requested total quantity increased by 1 in the EDI release that was received on March 4, 2013, and by 1 again on the next EDI release that was received after March 22, 2013.  The second and third lines of the output show that there was a little more fluctuation in the customer’s forecast, increasing in quantity, decreasing in quantity, and then increasing in quantity again.

An unfortunate problem may be present – what if the customer completely eliminates the forecast orders on their purchase order, but still sends in a header line for the forecast?  A future enhancement may be required, where the CONNECT BY LEVEL trick is used in the first half of the SQL statement (the current releases), just as it is used in the second half of the SQL statement (the historical releases), so that when the top half of the final SQL statement is joined to the bottom half, rows returned by the bottom half of the SQL statement are not unnecessarily removed from the output.

The output is a little ugly.  One approach to clean up the output involves spooling the output to an HTML file as explained here and in the documentation here.  Another approach to clean up the output involves sending the data into an Excel spreadsheet using either a macro or the Microsoft Query Wizard, accessed from within Excel (see the articles in the Excel category of this blog for an explanation of these approaches).

—–

The final solution for this analysis challenge is so simple when built up from smaller SQL statements as shown above; I wonder why I did not consider this approach 12 years ago?  :-)

Unexpected Timer Resolution, Unexpected Parked CPUs, Unexpected Power Consumption

April 19, 2013 (Modified May 11, 2013)

This blog article is not purely Oracle Database specific, yet it may have some relevance to companies that run Oracle Database on the Windows Server platform (for those DBAs lucky/unlucky enough to run Oracle Database on the Windows Server platform, you may find this article interesting).

I am in the process of setting up a couple of new Windows servers to perform various non-Oracle Database tasks.  I noticed that one of the servers had an odd issue – the server would occasionally become very slow at responding to mouse movements and keyboard input, for instance taking 30 seconds to move the mouse pointer a short distance across the screen.  These servers are running Windows Server 2012, which shares the same kernel and includes much the same features as Windows 8 – with the exception that the server operating system opens to the desktop rather than Windows 8′s new start screen.

Two years ago I wrote a brain teaser article that asked how it was possible that a 10046 extended SQL trace could output c=15600,e=510 on a line of the trace file when executing a SQL statement without using parallel query – essentially asking how it was possible to consume 0.015600 seconds of CPU time in 0.000510 seconds of elapsed time when the SQL statement was restricted to running on no more than one CPU.  In the comments section of the article I mentioned the ClockRes utility, but did not provide a link for the download of the program.  So, I thought that I would run the ClockRes utility on one of the new servers, make a change to the server, and then run the ClockRes utility again:

As can be seen above, on the first execution of ClockRes the Current timer interval was 1.001 ms, while on the second execution of the ClockRes program the Current timer interval was 15.626 ms.  There is an odd similarity between that 15.626ms time (which oddly exceeds the reported Maximum timer interval of 15.625ms) and the c=15600 reported in the Oracle 10046 extended SQL trace file.  So, what change did I make to the server between the first execution of ClockRes utility and the second execution?  For now I will just say that I stopped one of the background services on the server (more later).

I recall performing an experiment a couple of years ago with Oracle Database.  I downloaded a utility that offered to change the Windows default timer resolution from 15.625ms to 1.0ms.  That utility did in fact change the Windows timer resolution, resulting in Oracle Database outputting c= values in increments of 1000, rather than in increments of 15600.  If I am remembering correctly, a second outcome of the experiment was a decrease in performance of the test Oracle database on the computer due to the higher resolution of the Windows timer.

Could the change in the resolution of the Windows timer from the Windows default of 15.625ms to 1.001ms be responsible for the occasionally sluggish performance of the server?  One article that I found (and unfortunately did not save the link to) claimed that adjusting the Windows timer from the default of 15.625ms to a lower value, 1ms for example, could cause a significant negative impact in multitasking system performance (roughly 30% decrease, if I recall correctly).  I located an article on Microsoft’s website that offered some level of clarification, below is a short quote from the article:

“Applications can call timeBeginPeriod to increase the timer resolution. The maximum resolution of 1 ms is used to support graphical animations, audio playback, or video playback. This not only increases the timer resolution for the application to 1 ms, but also affects the global system timer resolution, because Windows uses at least the highest resolution (that is, the lowest interval) that any application requests. Therefore, if only one application requests a timer resolution of 1 ms, the system timer sets the interval (also called the “system timer tick”) to at least 1 ms. For more information, see “timeBeginPeriod Function” on the MSDN® website.

Modern processors and chipsets, particularly in portable platforms, use the idle time between system timer intervals to reduce system power consumption. Various processor and chipset components are placed into low-power idle states between timer intervals. However, these low-power idle states are often ineffective at lowering system power consumption when the system timer interval is less than the default.

If the system timer interval is decreased to less than the default, including when an application calls timeBeginPeriod with a resolution of 1 ms, the low-power idle states are ineffective at reducing system power consumption and system battery life suffers.”

The above mentioned Microsoft article also suggested running the following command from the Windows command line:

powercfg /energy

I had actually executed the above command before running the ClockRes program for the first time, and again after running the ClockRes program for the second time.  A very small portion of the powercfg generated HTML file follows, generated prior to the first execution of ClockRes:

Platform Timer Resolution:Platform Timer Resolution
The default platform timer resolution is 15.6ms (15625000ns) and should be used whenever the system is idle. If the timer resolution is increased, processor power management technologies may not be effective. The timer resolution may be increased due to multimedia playback or graphical animations.
Current Timer Resolution (100ns units) 10009
Maximum Timer Period (100ns units) 156250

Platform Timer Resolution:Outstanding Timer Request
A program or service has requested a timer resolution smaller than the platform maximum timer resolution.
Requested Period 10000
Requesting Process ID 536
Requesting Process Path \Device\HarddiskVolume4\PROGRA~2\APC\POWERC~1\agent\pbeagent.exe

This is the same section of the generated HTML file, generated after the second execution of ClockRes:

Platform Timer Resolution:Platform Timer Resolution
The default platform timer resolution is 15.6ms (15625000ns) and should be used whenever the system is idle. If the timer resolution is increased, processor power management technologies may not be effective. The timer resolution may be increased due to multimedia playback or graphical animations.
Current Timer Resolution (100ns units) 156261

That is potentially interesting.  The output of powercfg stated that PROGRA~2\APC\POWERC~1\agent\pbeagent.exe requested a timer of 1.000 ms, which then changed the Windows server system-wide timer to 1.0009ms.  Interesting?  PROGRA~2\APC\POWERC~1\agent\pbeagent.exe resolves to the “APC PBE Agent” service in Windows, which is a component of the American Power Conversion (APC) PowerChute Business Edition software.  That software interfaces with an attached UPS to provide a gentle shutdown of the server in the event of an extended power outage.  The “APC PBE Agent” service happens to be the service that I shut down between the first and second execution of the ClockRes utility.

Interesting?  Does that suggest that installing the APC PowerChute Business Edition software on a server potentially has a significant impact on the performance of that server due to the program’s insistance on changing the Windows system-wide timer resolution to 1ms?  A quick observation indicates that the change made by the APC software to the Windows system-wide timer resolution does NOT apparently affect the reporting of the c=15600 entries in an Oracle Database 10046 extended SQL trace when the APC software is installed on the server.  The question remains whether or not this APC software could significantly decrease the performance of that Oracle Database software (potentially by 30%, as suggested in the one unnamed article).

——

The Windows Server that is experiencing occasionally jittery mouse and keyboard input is reasonally high-end for a Windows server: Intel Xeon E5-2690 8 core CPU at 2.9GHz (with hyperthreading enabled, giving the appearance of 16 CPUs in Windows), 64GB of memory, RAID controller with 1GB of battery backed cache, 16 internal 10,000 RPM hard drives, two gigabit network adapters in a teamed configuration, etc.  It should require a substantial load on the server to cause the jittery mouse and keyboard input behavior.

The power option plan in Windows was set to High Performance, while the default plan in Windows Server is Balanced.  Various articles on Microsoft’s website state that the Balanced plan allows the server/operating system to use CPU speed throttling (reducing the CPU speed from the stated speed rating, 2.9GHz in the case of this server), and core parking (essentially putting one or more CPU cores to sleep) in order to reduce energy consumption.  Some articles on Microsoft’s site indicate that, at least with Windows Server 2008, that CPU parking may increase IO latencies - that, of course, would be bad if Oracle Database were installed on the server.  Other articles on Microsoft’s site indicate that there are bugs, at least with Windows Server 2008, related to core parking which causes the parked cores not to wake up when the CPU load increases.  I wonder if this particular bug is playing a part in the performance issue faced in this very recent Usenet thread that describes poor performance of Oracle Database running in Hyper-V on Windows?

Here is a screen capture of the Power Options window and Task Manager on the Windows Server 2012 machine that is experiencing occasionally jittery mouse and keyboard input (screen capture taken when the server was mostly idle):

Notice the inconsistency?  The server’s CPU is throttled down from 2.9GHz to just 1.16GHz while the power option plan is set to High Performance.  The Microsoft published “Performance Tuning Guidelines for Windows Server 2012” document on pages 16-17 states the following (I highlighted some of the words in red):

“Balanced (recommended): Default setting. Targets good energy efficiency with minimal performance impact.  Matches capacity to demand. Energy-saving features balance power and performance.

High Performance: Increases performance at the cost of high energy consumption. Power and thermal limitations, operating expenses, and reliability considerations apply.  Processors are always locked at the highest performance state (including “turbo” frequencies). All cores are unparked.

Power Saver: Limits performance to save energy and reduce operating cost.  Caps processor frequency at a percentage of maximum (if supported), and enables other energy-saving features.”

Well, that is interesting, and is inconsistent with the above screen capture.  Incidentally, when the server was experiencing the worst of the occasionally jittery mouse and keyboard input, the CPU utilization was hovering around 6% and the CPU speed was still coasting at 1.16GHz to 1.18GHz, the network performance hovered between 600Mbps and 1100Mbps, and the server’s internal hard drives barely noticed the traffic passing to/from the disks through the network interface (lower than 75MB/s and 137MB/s, respectively).  6% CPU utilization causes the mouse and keyboard input to become jittery?  With hyperthreading enabled, there is essentially 16 available CPU seconds per each second of elapsed time.  A quick check: 1/16 = 0.0625, so 1 (hyperthreaded) CPU at 100% utilization would be reported as a system-wide utilization of 6.25%.  Interesting, but is that statistic relevant?

I happened to have the Windows Resource Monitor open during one of the jittery episodes.  The Resource Monitor showed, shockingly, that 14 (possibly 15) of the hyperthreaded “CPUs” were parked!  That result is also in conflict with the Microsoft document mentioned above regarding “all cores are unparked” when the High Performance power plan is selected.  So, at 6% CPU utilization the server was CPU constrained.  Modifying the setting in the server’s BIOS that controls whether or not cores may be parked, so that the cores could not be parked, fixed the issue in Windows Server 2012 that resulted in the 30 second delay that accompanied moving the mouse pointer a short distance across the screen.

The server still exhibits a bit of jittery behavior with mouse and keyboard input when the server’s teamed network cards are heavily used for file transfers to the server, but at least the CPU activity is no longer confined to a single hyperthreaded “CPU”:

—

Considering that this server was ordered from the manufacturer as “performance optimized”, I am a bit surprised at the power consumption of the server.  The server was ordered with dual (redundant) 1100 watt power supplies.  With the CPU’s 135 watt maximum TDP (per Intel: “Thermal Design Power (TDP) represents the near maximum power a product can draw for a thermally significant period while running commercially available software.”), 16 hard drives, and 64GB of memory, I fully expected the server to consume between 700 and 900 watts of electrical power.

Here is the server’s power consumption when the server is lightly loaded with roughly 68 running processes (note that the server is connected to a 120 volt power outlet):

Here is the server’s power consumption when the server is moderately loaded with between 600Mbps and 1100Mbps of network traffic (the mouse pointer was slightly jittery at this point):

So, the server consumes 1.2 amps (126 watts) when lightly loaded and 1.4 amps (154 watts) when moderately loaded.  Keeping in mind that many of the popular incandescent light bulbs require 100 watts of power (note that some governments have now restricted the manufacturing of high wattage incandescent light bulbs), this server is consuming just a little more electrical power than a light bulb that might have been hung overhead just a decade or two ago.

One of the common arguments for server virtualization is energy savings – the above screen captures may suggest that energy savings may not be a significant cost-savings factor for virtualization with modern server hardware.  One might question how much energy is really being saved when the network interface is maxed out by a single virtualized server, just 6% CPU utilization results in a jittering mouse pointer, and there are eight to ten virtualized servers stacked on the physical hardware (all competing for the scarce CPU and network resources).

—

Added May 11, 2013:

Dell BIOS setting to enable or disable CPU parking in Windows Server 2012:

With the BIOS option set to enabled, disk activity caused by network traffic results in occasionally jittery mouse movements on the server.  Based on a bit of research, installing the Hyper-V role on either Windows Server 2012 or Windows 8 may disable CPU throttling and/or disable CPU parking.