Saturday, January 25, 2014

ASE, HANA and much more

After a long time I am back to writing this blog again. Much has happened in SAP ecosystem since my last post. SAP HANA has gone to cloud, ODATA has become the standard way of communicating between different layers in SAP products and SAP business suite customers are increasingly using Adaptive Server (ASE) as the underlying database.

As I continue to work on ODATA and ASE, new things continue to surprise me. These things, I call them quirks - may not be that surprising for an ASE veteran, but they are for users of some other databases in the market. These quirks/peculiarities or special features, whatever they are, have been discussed in various forums. One particular helpful resource I found is a creation of one of my co-workers. Check it out  (  http://www.sypron.nl/main.html ) to find wealth of interesting ASE facts compiled over the years.

Today, I will discuss a feature of ASE that an average user may not have come across. It's an sql command -SET CHAINED ON/OFF that controls the transaction behavior. If your code is not explicitly starting a database transaction for series of sql commands, then SET CHAINED OFF command tells ASE to start a transaction. In the jdbc code you can do connection.setAutoCommit(true) to get similar functionality. The chained mode is particularly important if you are trying to execute a stored procedure on ASE. The successful execution of ASE stored procedure is dependent on using the correct chained mode. What bugs me is that, as a user of the stored procedure you need to know which mode was used when that stored procedure was created in the database.

If you happen to use autocommit(true) while executing a stored procedure that was created with 'set chained on' setting, then you will get a nasty error that looks like this "this procedure may be run only in chained transaction mode, SET CHAINED ON will cause the current session to run in chained transaction mode" . I have seen countless posts on internet and recently in SAP ecosystem discussion forums about this error, highlighting the frustration experienced by developers new to ASE. Thankfully ASE provides a system stored procedure that can set the mode of a stored procedure to "ANY", which allows that stored procedure to be executed in both settings - autocommit true and false. However it's not used widely judging from the number of people that experience this problem. If you do not want to get bitten by this nasty problem in runtime you can choose to do either of these two.

1. If you have the access to the underlying database (you need to be the owner of the procedure or have an SA role) you can run sp_procxmode command to make the stored procedure in question run in any mode. Assuming the name of the stored procedure is sp_proc_1 the command would be
execute sp_procxmode sp_proc_1, "anymode"

2. You can do this at run-time in your JDBC code. Execute sp_sprocxmode procedure with only one argument - the name of the stored procedure. The result set of this statement will give you what mode this procedure needs. Assuming, it requires 'unchained', you can execute conn.setAutoCommit(true) and then execute the sp_proc_1 procedure.

The second option is the better one that will avoid certain headaches later on, if you ever want to execute a stored procedure in  ASE. Regardless of the mode in which the stored procedure was created, I recommend you implement this strategy. There are other interesting facts about stored procedures and why stored procedures are important again is something I would to write in my next post.


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