Merry Christmas CA

Well it is that time of year again when we all take a well deserved break (this is subjective I know), send those work clothes to the dry cleaners for a much need overhaul, eat too much, drink even more and come back to work refreshed in the new year with at least one broken new years resolution by the 5th of January.

Christmas is often a busy time of year for many of us and we sometimes also spend the time talking about those that are no longer with us at those family reunions. I presently have some of my relatives visting us and have also had a long time family friend popping in to say "Hi" even though we live 12,000 miles apart.

Anyhow, Christmas is a time of giving (well it is in my world) and CA thankfully think no differently.

If you haven't already seen the news feeds then you may not know that our friends at CA have gone GA on CA Plex 6.1. There are quite a few neat features in this release that are worthy of a mention here, highlights include:-

Model-based SOA support
- WCF Service Generation
More Extensible Development Environment
- Plex API Enhancements and Add-Ins
- Code Library Service Generator Plug-Ins
Windows Vista Support for development
Group Model Update History
Runtime Backwards Compatibility - Easy Upgrade from 6.0
- No re-gen or re-build from r6 to r6.1
Platform Compatibility Updates
- IPv6
- Java SE 6.0, ANT 1.7.0
- SQL Server 2008, Oracle 11g
- Windows Server 2008
- 64-bit Windows

For full details follow some of the following links (Note I am not responsible for external site content):-

http://www.ca.com/us/press/release.aspx?cid=194906

or the product brief

http://www.ca.com/files/ProductBriefs/ca_plex_product_brief.pdf

I am particularly keen on the additions and improvements to the Model API and what this will allow third party vendors to create to support the CA Plex ecosystem.

But then there is more.

CA have also announced that the user voting system polls used successfully in 2007 will be re ran early 2009 to help provide CA product management with user driven requirements for the enhancement of the toolsets (Both 2e and Plex). But remember you are voting in enhancement requests made. In order to get your requests in the list you need to contac CA support and raise a ticket.

But then there is more.

2e 8.5 is already Alpha and going Beta in the new year. Highlights for this release are:-

ILE Service Program support
- New object type to combine modules into service programs
- Supports CA 2E-generated and external modules
Web Services support
- Deploy ILE Service Programs as web services
- Based on IBM i Integrated Web Services server for ILE
Improved Impact Analysis
- Take account of commented-out code
- Voted No. 1 in 2008 Enhancement Request Survey
Better search/positioning facilities in the model
IPv6 compatibility
CA 2E Web Option Environments
- Separates user data from the product libraries

I believe GA is planned for July 2009.

But then there is more.

There are webcasts to be heard in the new year. There are events to attend. There are conferences to consider. There are powerpoints for CA world to be downloaded.

How do I know all this. Well I am a member of the PLC (Product Line Community) and as such I get regular email updates from the product management team at CA.

To join this ever growing list, simply click the link below.

http://causergroups.ca.com/usergroups/UserGroupHome.aspx?ID=391

Mery Christmas and a Prosperous (Credit Crunch Recovery) New Year.

Thanks for reading.
Lee.

2e and your support network

Updated - 12/06/2009

I recently received a communication via the blog feedback feature. It was from one of our colleagues in France who was a little concerned about the support he receives from CA and also the usage of the tools in general.

There are quite a lot of interweaving discussions to answer his question below.

"In France,we have CA/2E 8.1SP1fr RPG.Here,we have no news from this product,it seems dead! We have to contact US support to obtain some news/upgrades,it's very difficult to have a schedule of upgrades.We use 2E since 95 and nothing has changed in the way of using it. Please reply to discuss. Thanks. "

So I guess I need to answer each of these and share some opinion along the way. After all, isn't this the point of a blog in the first instance.

Is it Dead?

Well the short answer to that is "NO". A quite emphatic one actually. CA have a roadmap for the 2e product with a host of community voted enhancements being included in 8.5 (GA July 2009, I understand). I am sure these were discussed at CA World. There was also a call from Daniel Leigh recently to the community about utilising Web Services directly in 2e as well as catering for the creation of ILE service programs from within the toolset.

I have been part of the Alpha and Beta testing and these is certainly some good potential in these areas.

Keeping updated about the product.

CA is a big company and I would guess that the local offices are often the last to know about product centric announcements. The guys responsible for the 2E and Plex products are particularly vocal online and via a series of user groups. The US is the biggest installed base for these products so I guess it is only right that the focus starts states side. You can sign up to the forums, my blog and other fan sites as well as the Plex2E PLC (Product Line Community). Not to mention the local user groups in some regions. US and UK.

There is also Alpha and Beta testing programmes which I encourage you to consider.

Other useful links below which I have also added as a dedicated link on the blog home page.

The CA Forums

http://caforums.ca.com/ca/?category.id=caplex

Communities Product Line Community

http://causergroups.ca.com/usergroups/UserGroupHome.aspx?ID=391

Also check out the other links I have on the blog home page. I link to the Plex and 2e Wikis which are resources we can all contribute to as well as specialist sites of key CA product partners.

Once you are a member of the PLC you will receive very regular updates from Bill Hunt and the team as well as invitations to webcasts.

And then you always have the other forums around the platforms the tools generate for. i.e. SystemiNetwork, although I guess this will be changing its name again soon once the Power System branding gains momentum.

Upgrades.

CA have explained in the past on numerous occassions and the release schedule would confirm this, they issue major upgrades for the products every two years. Service packs in between which add functionality as well as a fix roll up. See the CA website for more details about each of the product roadmaps along with release and support cycles.

On a side note SP2 has been available for quite a while (November 2007) and as I referred to earlier 8.5 is GA for July 2009.

Features introduced into 2e in recent years.

The following link (on the 2e wiki) highlights the changes that have been added to 2e in recent years. If you are considering or using Plex also then you should check out it's wiki also. See the links at the top of the blog.

http://wiki.2einfo.net/index.php?title=Versions

Depending on how you use the tool or how you have approached extending the tool would dictate which of the features you are using. Often, as the tool has been around a while we just use it as we always have. Not too different to those of us who use Word as if we were using Word for Office 4.3 instead of 2007.

If you are into componentisation of your 2e systems then you will be utilising many of the other features. However, there is no right or wrong way to use the product, simply what works for you. But do take a look at what is there and see if the new features can be applied to your environment.

I was quite shocked to see on a recent PLC 2E users survey that many shops are still on 7.0 and some on earlier versions.

My strong and hence bolded recommendation here is to get current.

Certainly 15 years ago the focus was that 2e generated every aspect of your system. Nowadays if forms part of a hetrogenous platform of servers and tools.

The base tool has remained largely the same with the focus on value add but 8.5 has quite a few base tool enhancements. I like the filtering now. Very neat. And recent releases have had quite a lot of neat shortcut function keys and subfile options that can increase developer productivity.

Lastly, I guess there is also the advent of the internet. With so much information available, if we are not sourcing our information via the net then we could be missing out on lots of it. And if we looked closely or joined the PLC you would know about the 4th Annual conference taking place in Ft Lauderdale, Florida, USA in September 2009.

www.plex2e.com

Thanks for reading.
Lee.

What next?

My regular followers for which there are many. I am pleased to say that I have over 100 unique visitors per month visiting the blog and the number is increasing. If have dabbled with a mixture of real life stories and content, technical 2e content, management styles, observations about software development and a couple of other stories related to me and my experiences as long as there is a loose IT twist.

I have spent much of the last two months writing more about 2E. I plan to finish off my posts in this area over the coming months and years. I certainly have plenty of material left.

Finish 2e Development Standards
Model Management
Database Adminstration Guides
Advanced Development Techniques
Model Tidy
Modernisation Options for 2E generated systems

Plex Development

........ are all blog series candidates in their own right.

I thought that I'd take a week off this week and ask you the readership what you would like to see. The hits to date make it a worthwhile exercise for me to put this content on the web. If you have any content you wish to share, requests for additional coverage then place a comment on the blog and I'd be happy to start doing some of this for you.

So.

Let me know. I reckon I have a year or two left in me looking at my current roadmap. A little more now won't hurt.

I look forward to hearing from you.

Thanks for reading.
Lee.

2e Development Standards - (Composite Functions)

Todays topic is composite functions.

I have said before that there are many ways to skin a cat and with development regardless of tools and languages used, it is no different.

To date I have concentrated on the generic principles of development and also on the CA 2E tool from Computer Associates. I have put quite a few posts in place around 2E with many many more to go. To be honest I am less than 20% through what I intend to post from the technical perspective and I have barely touched the Plex product. Still good things come to those who wait.

http://www.dictionary.com/ has the definition of 'composite' as "made up of disparate or separate parts or elements". In 2E terms it means the linking of two or more functions to serve a business purpose. For example to clear a file using 2e function types you may either call a EXCUSRPGM and use the operating system or you may chose to use a RTVOBJ with no restrictor/positioner keys and then call a DLTOBJ for each record in the file. You could also call a SQL routine, embed the OS400 command in a message etc etc etc. You get my point. The composite in this example is the RTVOBJ/DLTOBJ combination.

There are other composite types that are more often encountered. Especially around creating or changing records in a database file (table for the SQLites amongst you).

I have created functions named CRT/CHG or CHG/CRT to solve a common problem of what do do if the record does or does not already exist in the database.

This lead me to consider is there is a preferred default method and are there any variations. Once again a big thanks to Ray for his contributions here.

CHG/CRT v CRT/CHG

There are times when if a CRTOBJ fails due to the record already being in existence or a CHGOBJ fails because the record does not exist. To solve these issues we generally create combination functions named either CRT/CHG or CHG/CRT. Or if you follow my recommended standards and if these are default functions then they would be named *CRT/CHG or *CHG/CRT.

In general you should select the one that is most likely to succeed, so depending on your knowledge of the environment and the data being processed, if the record is likely to not be there then you need to use the CRT/CHG combo.

There are some performance considerations over and above the availability or otherwise of the underlying record.

A CHGOBJ that contains a CRTOBJ if a record does not exist is inefficient as it generates the following code. This is particularly true for SQL generation.

Pseudo SQL Code

DECLARE CURSOR FOR UPDATE
FETCH
UPDATE if record found
INSERT if no record found
CLOSE CURSOR

Pseudo RPG Code

CHAIN
UPDATE if record found
SETLL & INSERT if no record found

An alternative coding style with a CRTOBJ calling a CHGOBJ if record already exists will generate the following code. The CHGOBJ must be an 'update style' that does not use a cursor.

Pseudo SQL Code

SELECT by key
INSERT if record not found
UPDATE if record exists

Pseudo RPG Code

SETLL
WRITE if record not found
CHAIN & UPDATE if record exists

A CHGOBJ with a little bit of grunt.

To create an 'Update style' CHGOBJ:-

For performance reasons we need to omit the prior SELECT generated for SQL CHGOBJs. This is mainly for CHGOBJs called repeatedly in batch type processing. But it can only be done if there is no requirement to read existing DB1 context fields. To do an immediate update we need to create a special version of a CHGOBJ called an UPDATE function. This will have following characteristics:-

1 - Ensure that there is no coding inside the CHGOBJ. Commonly we must transfer the timestamp coding from inside the CHGOBJ to input parameters and setting the timestamp fields directly on the CHGOBJ call.

2 - Ensure that the CHGOBJ parameters are defined in the default way using the UPD ACP structure. Fields that do not need to be changed should be made NEITHER parameters.

3 - The CHGOBJ function option for Null Update Suppression should be = No. This ensures that there is no attempt to perform an image check.

4 - UPD style CHGOBJs should ideally only have the attributes that are being changed. This is particularly important when calling a CHGOBJ from inside a RTVOBJ over the same file. Passing in DB1 context for those filed not being changed is not conducive to performance since the optimiser cannot differentiate between changed & non changed attributes.

Thoughts, opinions, concerns or fanmail gratefully accepted. Cash donations to charity please.

Thanks for reading.
Lee.

2e Development Standards - (Hints and Tips DLTOBJ)

The humble DLTOBJ is the topic of this weeks post. This finishes of the series on the main 2e internal function types. I have covered the RTVOBJ, CRTOBJ and CHGOBJ so far. Next weeks post will be about the mertis of using a CRT/CHG or CHG/CRT combination function.

Following that I will be blogging about standards for EXCUSRSRC, EXCUSRPGM and the EXCINTFUN/EXCEXTFUN function types before moving on to a series on the screen function types.

So plenty to get though over the next few weeks. For those of you following the series, bare with me as I get these completed and published.

Back to todays topic. The delete object (DLTOBJ).

General considerations.

Only one DLTOBJ, the default (*DLT), should be present on any file. It will have no action diagram coding added.

If other associated files must be deleted or updated at the same time as the DLTOBJ. An EXCINTFUN or RTVOBJ should be created as a standard wrapper and named *DLT (Cascade).

You can use a DLTOBJ to clear an array. Simply create the DLTOBJ function over the array and remove all keys. Note this technique is not applicable for files. You should prefix the array clearing delete with CLR. I.e. "CLR Standards Sample" dropping the ARY prefix from the actual array. Note: If using the Cobol generator then this is inefficient and you are better to use the traditional RTVOBJ/DLTOBJ approach.

Auditing at record level. Remember that you no not need to add auditing records for any entry you are deleting.

Gotcha's

It is not possible to suppress the error message if the record to be deleted does not exist. Therefore if the DLTOBJ is conditional it should be called from a RTVOBJ based over the same file. Note: If called directly then the *Return code must be set to *Normal as deleting a record that is no there is generally not considered and trapped as an error.

Thanks for reading.
Lee.

2e Development Standards - (Hints and Tips CHGOBJ)

Another post about some of the finer points for the internals functions available in the 2e tool. I have covered off the RTVOBJ and CRTOBJ in some detail. I have left the obvious stuff for the user manuals and am really covering off best practices and gotchas in these sections.

Any observations and comments are gratefully received and a big shout out to Ray Weekes who passed on many of these in these sections from his experience.

The default CHGOBJ will have all parameters open except for Time Stamp and any other derived attributes which will all be made NEITHER. Action diagram coding added will only be for Time Stamp and derived data i.e. Audit records or calculated values.

Further CHGOBJ functions may be created where only subsets of attributes are to be changed or where special processing is applicable. All CHGOBJs should replicate the standard support for Time Stamp and derived data where appropriate.

Structuring your parameters. There are 2 methods for defining a CHGOBJ where only subsets of attributes are to be changed. The default method uses the UPD ACP RCD defined over the first parameter block line as the input parameter list. Database attributes not to be automatically changed from input parameter fields are set to NEITHER.

The second method uses the UPD ACP KEY as the first input parameter list line. The UPD ACP RCD is then optionally used on the second parameter line. This second approach suppresses any automatic update to the DB1 context and therefore requires a *MOVE ALL PAR to DB1 to be added to USER:After DBF Read. This KEY method has the advantage that no NEITHER parameters need be defined and no unnecessary coding is generated for NEITHER parameters.

It also protects the CHGOBJ from the effects of future attributes being added to the file.

The default RCD method of a defining CHGOBJ is sufficient for most small files or where most attributes are being replaced. The KEY method is preferred for large files where only a few attributes are being changed. It is also the preferred method on any file where existing database attributes are being incremented rather than replaced with new parameter input values since it makes the action diagram coding simpler. E.g. A CHGOBJ designed to get the next surrogate# to be used.

General pointers.

It is possible to suppress the default error message if the record does not exist by setting PGM.*Return Code = *Normal in USER:Record Not Found. Alternatively you may add a call to a CRTOBJ over the same file. But if the CRTOBJ is conditional then still set PGM.Return Code = *Normal where CRTOBJ is not called.

Any UPD ACP RCD parameter field defined as OUPUT or BOTH will be automatically moved from DB1 context to PAR context after the database update. This allows a CHGOBJ to also function like a RTVOBJ GET and to return current database values.

When using a CHGOBJ to increment values on a database remember to move the current DB1 values to a holding field as the PAR to DB1 move will overwrite the original values. Then in the Process before Update you do the *ADD arithmetic. A good standard could be to prefix the function like UPD nnnnnnnnnnnnnn.

Null update suppression is the preferred choice for all CHGOBJs. Model value YNLLUPD=*AFTREAD. This means that an image check takes place after USER:After DBF Read. The USER: Before DBF Update is only executed if the record image has been changed. Time Stamp logic and other derived processing must therefore be in USER: Before DBF Update.

In general do not use a CHGOBJ to change the primary key. Although this technique works in RPG it causes problems in COBOL. However, it may be used in RPG & SQL. SQL CHGOBJ requires the key fields to be set to MAP to force them into the SET clause.

Gotcha's

You must never *QUIT from a CHGOBJ since this may leave a lock on the record. Use PGM.*Record Changed = *Yes if any conditional processing is required inside the CHGOBJ.

Do not use a CHGOBJ or DLTOBJ over a PHY ACP because of a bug in the 2E SQL generator.

Next time the DLTOBJ.

Thanks for reading.
Lee.

2e Development Standards - (Hints and Tips CRTOBJ)

Here we go again. Another in the series around 2e development standards. Today I thought I'd cover the CRTOBJ function type and share what I have gathered on the road over the years.

Cutting straight to the point.

Keep numbers to a minimum. In general there should only be one CRTOBJ, i.e. The default (*CRT), per file. This will have all or most parameters open and will not contain any complex processing. This makes the function reusable. The exception being surrogates that are generated inside the function and control fields like audit stamps.

These will generally be set to NEITHER and primed inside the function.

The exception to one per file would be for files that are archived or image copied. But this would not in general usage be the default *CRT. I.e. CRT Archive Image.

Shielding developers from the parameters. For simple files where records are only created under standard application control then time stamp fields may be set as NEITHER parameters and the DB1 context primed inside the CRTOBJ. Similarly, where an internal surrogate number is generated as part of the primary key then an appropriate function call over another file may be inserted. The surrogate number will normally be NEITHER, but it may be OUTPUT or BOTH if required for lower level files.

Wrappering the CRTOBJ with an internal. In some cases there may be a hierarchy of EXCINTFUN calls. Each call then performing some specific function at one level before calling the next level. This may be necessary, for example, because associated files have to be updated when a new record is created. Each main line request to create a new record will call the EXCINTFUN appropriate to the level of complexity required. If requiring just an image copy then it will call the CRTOBJ direct.

An EXCINTFUN designed to participate in the create process should have its parameters defined using the UPD ACP RCD, similar to a CRTOBJ.

Be aware of the probability of a records existence. Where it is not clear whether a record exists for a given primary key then it may be necessary to define a special CRTOBJ i.e. CRT/CHG, which suppresses the error condition and optionally changes the record. I will post a CHG/CRT v CRT/CHG vs RTV/CHG or RTV/CRT debate once I have covered off the intricacies of each of the four main internal function types.

Gotchas

To suppress the error message & error condition if a record already exists then a CRTOBJ may be created where the PGM.*Return Code is set to *Normal in USER:Record Already Exists.

Alternatively if a record already exists and it is appropriate to change attributes then a call to a CHGOBJ may be inserted in USER:Record Already Exists. In this case it is important to ensure that the parameters passed to the CHGOBJ are PAR and not DB1 context.

It is very important in any CRTOBJ to ensure that the DB1 context for any fields not directly input by parameters are initialised or primed with data inside the CRTOBJ. (They will not be input if they are set to NEITHER or if the parameter definition is changed to KEY). There is no automatic move from PAR to DB1 for NEITHER parameters and the DB1 context may contain old data from previous database functions.

By default a SQL CRTOBJ will not check for duplicate records if there is no coding in any action diagram user point other than ‘Processing Before Data Update’. However, there are times when you must or it would be better if you did check. This is accomplished by inserting code, such as comments, in ‘Processing if Record Exists’. This also suppresses the error message if the row already exists.

Next up. The CHGOBJ.

Thanks for reading.
Lee.

2e Development Standards - (Hints and Tips RTVOBJ)

I thought I'd have a break from the 2e naming conventions thread that has occupied most of the last month and launch into a series of smaller posts that talk about some of the hints and tips associated with the 2e function types.

Today's topic is the RTVOBJ. One of the most useful function types in 2e. One which is often misused or understood.

The following are some hints and tips I have learnt, taught, embellished and/or stolen over the years.

RTVOBJ Tips

Naming. Most RTVOBJ functions can be divided into one of two types. Single record GETs to bring back attributes for a given key value. Multiple reads to perform some sort of process logic or test. Different naming conventions, 'GET By ...' or 'RTV Last four transactions' will identify these two types. See previous post re:naming standards.

Getting Records. A GET will be based upon an ACP with a unique key, usually the RTV and pass in a fully RST key value. The function will only return database attributes + the xxx Record Found Y/N flag (optional for your site). The return code will not typically be explicitly modified. If the record is not found then output parameters must be cleared. Parameters, both INPUT key fields and OUPUT attributes should be defined using the same access path (ACP) that the function is based upon. Avoid using the individual field definitions unless they are not scoped by an access path.

On certain files with fixed key values the RST key may be set to NEITHER and primed inside the RTVOBJ at initialisation. Examples here are system tables that have one record.

GET's will return ALL attributes including spare fields. (A future post will talk about the benefits or otherwise of using spare fields). If the standard *GET will do, then use it!!!. There may be other ‘Get xxxxxxxx’ functions currently in your models which may have a subset of the fields. You can replace with a single *GET if preferred.

Other types of RTVOBJs will perform various processing requirements over multiple records these could be prefixed as RTV.

General Hints. When testing for certain conditions you should *QUIT the RTVOBJ for performance reasons once the condition has been found thus minimising I/O and decreasing function runtime. There are exceptions here for *Arrays. (future post).

In general try to avoid changing the default PGM.*Return Code setting, although there may be circumstances where this is justified. If you do need to identify a specific condition other than normal the user CND.*User Quit Requested appears to be a standard I have seen at many companies.

If the RTVOBJ is built over a RSQ ACP and uses RST/POS key fields then explicitly define the key fields using a KEY structure. This will allow the developer to zoom into the key structure and understand what the key fields are.

Do not leave the fields as MAP. There is no relevance for a RTVOBJ and it only confuses new developers. CA please change this. I know it doesn't generate anything!!!!!!

Default RTVOBJ's i.e. *GET should have parameters passed as RCD. Get By and RTV's over alternative access paths should use the KEY/RCD method.

If using a RTVOBJ to retrieve reference data. It is best to not do the call if the value is optional. Saves an unnecessary I/O.

Gotcha's

Best Practice

There is a well-known bug (feature) in a 2E generated RTVOBJ in that USER:Exit Processing is executed if no records are found and there is no coding inside USER:Record Not Found. Therefore if any action diagram coding is added to USER:Exit Processing then you must also code something (comment or *QUIT) inside USER:Record Not Found. This ensures that the function always behaves in a predictable manner.

If the data passed in as RST or POS parameter is of a different domain and is alphabetic for a shorter length then unpredictable results may occur. This is because the generated code is failing to clear fields when building the RPG key list. – I could not replicate in the latest release.

Best Practice

If you change the ACP that the RTVOBJ is based upon then also remember to change parameter definition. It is best to keep these consistent for developer readability.

Version 7.0 of 2E allows RTVOBJ's to be written over physical files. This reads the file in relative record number order. This is quicker than using a logical. This technique is useful when you need to read an entire file. A fix program would be a good example.

I will cover CRTOBJ in the next blog posting.

Thanks for reading.
Lee.

2e Development Standards - (Further Naming Conventions)

So here we go. Another part in the CA 2E development standards series. Here I discuss/publish some naming conventions I have found useful with common functions in a 2E model.

I have worked at a few sites over the years that have varying levels of standards applied to the model and different approaches aiming to solve the same problem.

I have worked at sites that like to use an incremental prefix i.e. RTV56 etc, some that leave the defaults and others that follow naming convention prefixes. As with any standard it is not the actual standard that it is important. The area of concern for any development shop is the continued adherence of the standards.

What I have found works best for me is to use a common set of naming standards for the core functions in a model. Today we will discuss core functions and their naming conventions.

I will finish with a couple of examples of why I settled on my approach for 2E naming standards and as always I expect these to cause some debate in the community.

Default Create Object

I prefer that the default create object (CRTOBJ) on a file is named as '*CRT'. This function will have all the relevant processing that is appropriate to the most common use of the function. Some shops will have auditing and others use surrogate systems. The default will be named as above but other variations may be named 'CRT with Audit' or 'CRT (No Audit)'. However, if most of the time you only need to perform your sites default processing when creating a record, the '*CRT' is much easier for everyone to remember.

The important fact here in the *CRT means the default behaviour. The others are variations and are therefore not classed as default functions and will be named slightly differently. i.e. without the *. The CRT prefix should remain.

As only one function of any name can appear on any file, for *Arrays the standard is extended slightly to be '*CRT Array name' as all arrays share the same file. They simply use different definitions for the access path (sorry, array structure).

Default Change Object

Follows the same rules as the create object but will use *CHG and CHG prefixes as appropriate.

Default Delete Object

Follows the same rules as the create object but will use the *DLT and DLT prefixes as appropriate.

Also a *DLT (Cascade) can also be created. This will actually be based on a RTVOBJ and will delete all child records before deleting the parent key. Thus reducing orphaned records.

Default Retrieve Objects

As a retrieve object (RTVOBJ) can be used in many ways. I will refer to the two most common usages. The fetch of a record and the checking for a record's existence. Also remember that a RTVOBJ is also used for processing files. The next two default functions are based on a fully restricted key.

I have used the *GET naming convention for a full record being fetched. This function will be based on the default retrieval access path. Variations that bring back fewer fields or use an alternative access path will begin with GET. If using another access path use the standard of 'GET By Access Path Name'. If getting a subset of fields use the 'GET subset' - replace subset with a meaningful description. Once again I am highlighting the default usage of this function type.

I have worked at one site that prefers to bring back a Record Found Y/N flag rather than use the return code. This is site specific and I'll leave you to decide on the correct usage of the flag versus the *Return Code. See my other blog which provides further details.

Another usage of the RTVOBJ is for checking for the existence of a record. I have seen this implemented as either a *CHK or and *XST. Either are fine as long as you are consistent.

Again, note that for both of these functions types the array version will need to supply the array name as a qualifier.

There are a further two usages of the *GET and *CHK/*XST function type. This is only related to files that use the 'Qualified By' file relation to describe the key. You will know that the 'Qualified By' is used for file structures that may have a term or a date to identify a value in the key. i.e. A product price file might be qualfied by a field like 'Product Effect Date'. This saves you having to have a record for each day that a price is valid.

You will also know that this relation will automatically read backwards or forwards to find the correct record. Note this only works for the default retrieval access path. Therefore a *GET or the *CHK/*XST will generally find a record but your business logic is trying to determine if a record exists for the actual date. There are several ways to do this. You can either create an alternate RTV access path and write a 'GET By RTV 2' type function. This is perfectly reasonable.

However, and there always is one, I would suggest that a function named '*GET (Exact)' which is only used for files with a 'Qualified By' relationship will do additional processing to determine if the KEY is equal to DB1. This will help to identify to a developer when they are programming, that the file has a 'Qualified By' key but also negates the need for an unnecessary access path to be created.

This pretty much summarises my recommended standards for internal default functions. There are a couple of regularly used external function types that might also be useful and form part of my DBA recommendations of functions that should be created for every file.

The rule of thumb for creating default functions should be.

All Files - *GET, *CRT, *CHG, *DLT, *CHK/*XST and *GETEXT.
Files with a qualified By - *GET (Exact) and *CHK (Exact)/*XST (Exact)
Reference Files - '*SLT filename'
Parent/Child - *DLT (Cascade)

Default External Functions

The *SLT function is named this way as it will be used by the generator when building implicit field prompting code. The routine is also used to validate a record existence in relation checking. As such a default select must be first on the file and also never have its parameter interface changed unless the keys to the file changes.

The *GETEXT (An EXTEXFFUN with a parameter interfaces the same as the *GET) is often used for several reasons.

RPG Limits. Used to limit the number of subroutines or files in a compiled program, not a fully recommended reason. There are other specialist reasons why you would want to use this routine.
Cursor awareness. Wanting to re-read an access path whilst reading the same access path. , therefore not corrupting the cursor.
Externalisation or Program API. Externalising a RTVOBJ function for use within a non Synon environment i.e. CL Program.

If externalising based on another access path call the function 'GETEXT By access path'.

Best Practice

If creating these functions ask yourself this simple question. Am I creating this because of a file limit and if so, is this really the best section of code to externalise? Remember reducing a program from 51 files to 50 (so it compiles) only leaves a maintenance issue for the next developer, and it might be you. Afterall, there is nothing worse than seeing a string of externalised RTVOBJ functions.

Summary

I have generally preferred a prefix and/or suffix when naming functions. The prefix has been used to identify format of the function and the suffix as a sub group. This will become clearer as you see the examples build up on this blog.

You will notice that some are prefixed with an asterisk (*). This is usually reserved to indicate internal Synon objects in a model. I have chosen to indicate my core functions using this method because the * for default function types means that are all grouped them nicely on pick lists. This is done to ensure that they appear at the top of the list of functions. I am aware of other sites using numeric or other acceptable characters to attain the same result.

Note: If you choose to use this approach a known issue is that searching for a *CRT in the open functions screen doesn’t work. This is the only known limitation of this approach from a technical perspective. Other may well say that this encroaches on 2E objects. I fully agree that files should not start with * but the odd function that is core to your development model, no worries.

My next 2e naming conventions post will focus on ideas for other non-default functions.

Thanks for reading.
Lee.

2e Development Standards - (Extra Naming and General Standards Part 1)

Continuing with the series on 2E development standards.

A model-naming standard is very important, particularly for large models, to aid understanding and navigation. There are several types of naming standards to consider.

Model Names

A CA:2E data model has a 25-character object text names associated with files, access paths, fields, field conditions, functions and messages etc. The guidelines for each object type are detailed below. As a general rule:

Apart from files, try and only use 24 characters for the field, function, access path etc. This make it a lot easier to navigate around in the model and to use the ‘?’ prompting facility.

Capitalise all words except articles, prepositions, conjunctions, and the 'to' in infinitives. E.g. 'Currency of Invoice'

Avoid punctuation.

Try to establish a vocabulary of preferred names. Where abbreviations are necessary then they should conform to a common abbreviations list. It is recommended this list be generic across all of your development models and other languages and environments.

OS/400 Object Names

OS/400 object names and DDS names are required for actual implementation. CA:2E will assign names for all object types according to its own naming standard. Messages, DDS format names and fields will default to CA:2E assigned names.

If using a Multi-Version Multi-Model setup extra care needs to be taken to ensure that and new model objects are created equally if coding into multiple models i.e. Bug fixing a current and development release at the same time.

Queries can be written to keep tabs on objects and their names that do not cross reference satisfactorily. I.e. Model Name to Model Name as well as Implementation Name to Implementation Name. This forms part of a wider blog on model management techniques. Something for the future?

Some development shops have chosen to replace the 2e naming conventions for some objects in a development model. The Pro’s and Con’s of this approach are as follows:-

Pro's

Nicely named objects. Great for when calling programs from a menu or command line.

Encourages a standard form and reinforces the principle of the naming conventions.

Easy to detect if not renamed as 2e prefix is still associated to object.

Con's

After a while it is difficult to get a unique and meaningful object name, therefore, some names can seem ambiguous.

Extra work for a developer. Often forgotton.

Will generally require a mnemonic standard i.e. XXYYYYnnZ so may as well have the defaults.

Model Files

All new files and file changes should be managed by the Database Administrator (DBA) or a central owner for that model. This of course, depends on the size of your development shop but it good practice to separate the roles. This will allow good control of the model.

Implement a TLA?. I have implemented a Three-letter Acronym (TLA) following the name at some sites I have worked at. E.g. ‘My Sample File MSF’, The TLA will occupy the last 3 bytes of the available space for the file. Note this is the only model object type where I have deliberately use the last byte.

These 3 letters should precede all fields for that file.

File descriptions should represent a single instance of an entity, e.g. 'Customer' not 'Customers'. However, if the name describes many attributes of a single record then a plural may be ok, e.g. 'Account Parameters'.

Avoid using descriptive names like 'Details' or 'File'. E.g. 'Customer' rather than 'Customer Details File'. However, sometimes it may be necessary to differentiate between different levels of detail, e.g. 'Order Header' and 'Order Line'.

Short names will avoid truncation when assigned by CA:2E to default DBF functions or foreign key fields using 'For' text although the DBA processes of replacing or renaming of fields should negate the need for the developer to be to concerned.

Try to group Parent/Child file relationships by using common name prefixes.

Future blogs will expand on the area of model management and database administration guides.

Access Paths

Unlike files, access paths can be created by a developer with *PGMR access. It is recommended that you query the 2E model files and keep an eye on any new access paths that are created and their purpose. These should be reviewed from time to time to ensure that best practice has been considered when access path was created.

Do NOT create new access paths without thinking if there is an alternative e.g. Using one that is similar and/or doing selection within the functions. If in doubt, talk it through with your DBA or a senior developer.

Virtuals should, in general, not be used, and should NEVER be on standard access paths. There may be times when they are the best solution e.g. For resequencing a query access path rather than creating a work file.

The description should try and explain the purpose of the access path.

In general there should only be 1 UPD (Update) style access path per file.

In general access path relations should NOT be dropped. If this is used then the default access paths should be clean and an alternative RTV or RSQ created.

No Virtual Virtuals. Avoid multiple nested levels of virtual fields if you are going to use them.

It is highly recommended that default access paths should never contain Virtuals or have Select/Omit. Use an alternative RSQ or RTV if virtual fields are deemed necessary.

If creating an access path over an assimilated file from another model then care must be taken with the default naming of the access path.

Next time we will talk about functions and I will provide some recommendations for naming standards as well as some standards for default functions.

Thanks for reading.
Lee.