Excel output is valid option for concurrent programs in R12.1.3, but it is not true excel output.
This is known issue with XML Publisher RTF Template output to EXCEL. XML Publisher RTF template does not generate native excel version. It generates HTML version of excel version (not binary xls). That is the reason Excel Output files are huge. We can see that the data is formatted using HTML tags, if we edit any of excel concurrent program output files on the unix server. This is restriction with R12.1.3 or lower versions.
Only workaround is to use EXCEL Templates to generate the report output to Excel, But R12.1.3 doesn’t support Excel templates. Excel templates are supported in R12.2.3 and later.
To overcome the file size issue in R12.1.3, we can create text version of the report with CSV and the file size is small. The output file is plain simple text with comma separator, but it looses some excel native formatting like loosing decimal zero etc., We can use some workaround to keep decimal zero, if the report has applicable column(s).
Reference Oracle support notes:
https://support.oracle.com/rs?type=doc&id=760437.1
https://support.oracle.com/rs?type=doc&id=2206951.1
Text Output with CSV is opened directly in excel but it is in a single column. User has to apply “text to columns” excel feature to separate the columns. I implemented the solution for couple of reports when we had file size issue with excel output files.
Note: Generating Huge excel output files is an issue at the server level as well. System will have space issues because of huge output files.