Algorithm #3

CHANGE and ADD transactions; Several transactions per master

record

1Prepared by Perla P. Cosme

Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) { make a change in the master record output master record in new master file Get_Next_Trans Get_Next_Master } else { print “no matching record in the master file” Get_Next_Trans }

Recall Algorithm #1

2Prepared by Perla P. Cosme

Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) { make a change in the master record // output master record in new master file Get_Next_Trans //Get_Next_Master } else { print “no matching record in the master file” Get_Next_Trans }

Recall Algorithm #2

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Think about this ….

If Algorithm #3 is to include ADD transaction on the existing CHANGE transaction in the Algorithm #2, then when are we allowed to ADD or create a record?

a. Master key < transaction keyb.Master key = transaction keyc. Master key > transaction key

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Think about this ….

If Algorithm #3 is to include ADD transaction on the existing CHANGE transaction in Algorithm #2, then when are we allowed to ADD or create a record?

a. Master key < transaction keyb.Master key = transaction keyc. Master key > transaction key

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Why (c)? Justify.

Justification why the Answer to the previous Question cannot be (a)

Let us prove by citing an example:MF: 6 7 8

TF 8 ANote: if master key (7) < transaction key (8), and the

transaction is ADD, you might add a record whose primary key is the same as the one you are about to create/add.

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Justification why the Answer to the previous Question cannot be (b)

Let us show one typical example:MF: 3 6 11

TF: 3 3C A

Note: if master key (3) is equal to transaction key (3), you will be creating duplicate records in the master file. (The master file should never have duplicates.)

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Question: How should Algorithm #2 look like now to reflect the error in adding a record when master key = transaction key?

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Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) {Case update_code ‘A’: print “duplicate record” Get_Next_Trans ‘C’: make a change in the master record Get_Next_Trans Default: print “invalid update code” Get_Next_Trans } else /* no matching record in the master file */ { print “no matching record in the master file” Get_Next_Trans }

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Justification why the Answer to the previous Question is (c)

• It is in the third case (i.e., master key > transaction key) where we are allowed to add a new record. Hence, it will be in such section of the algorithm where we are going to concentrate making the modifications to Algorithm #2 to fit to our new requirements – CHANGE and ADD transactions with multiple transactions per master record.

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Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) {Case update_code ‘A’: print “duplicate record” Get_Next_Trans ‘C’: make a change in the master record Get_Next_Trans Default: print “invalid update code” Get_Next_Trans } else { // no matching record in the master file print “no matching record in the master file” Get_Next_Trans }

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This is the Algorithm #3 that explicitly

includes the error-handling routine

when master key is equal to transaction

key

Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) {Case update_code ‘A’: print “duplicate record” Get_Next_Trans ‘C’: make a change in the master record Get_Next_Trans Default: print “invalid update code” Get_Next_Trans } else { // no matching record in the master file print “no matching record in the master file” Get_Next_Trans }

12Prepared by Perla P. Cosme

These two (2) lines will still be

maintained but only when the update

code is C.

We shall introduce a function called NOMATCH

to handle the ADD transaction and the

succeeding ADD and/or CHANGE transactions on the same newly created

record.

Get_Next_MasterGet_Next_TransWhile NOT (master_key==sentinel AND trans_key==sentinel) if (master_key < trans_key) { output master record to new master file Get_Next_master } else if (master_key == trans_key) {Case update_code ‘A’: print “duplicate record” Get_Next_Trans ‘C’: make a change in the master record Get_Next_Trans Default: print “invalid update code” Get_Next_Trans } else { // no matching record in the master file NOMATCH }

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Function NOMATCHCase update_code ‘A’: Build new record from transaction record new_key = trans_key Get_Next_Trans while (trans_key != sentinel AND trans_key == new_key) Case update_code ‘A’: print “duplicate add” ‘C’: make change in the newly created record Default: print “invalid update code” Get_Next_Trans output new record to new master file ‘C’: print “no matching master record for transaction key” Get_Next_Trans Default : print “invalid update code” Get_Next_Trans

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These are the lines that were retained from Algorithm #2.

Let’s simulate the SFO using Algorithm #3

We shall use the same example as what we presented previously.

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The Third AlgorithmCHANGE and ADD transactions;

several transactions per master record

MF 3 6 10 11

TF 3 3 11 11 11 11 18C A A C C A A

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Questions? Comments?

Suggestions? and Open Forum

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