Naming convention of .unl files - export

Question

I would like to understand which is the rule that is applied for the naming convention of the .unl files generated once I use dbexport on my Informix database.
I understand that:
+ Each file refers to a different table
+ Each file uses 5 letters and 5 numbers (example: tbabc01234.unl, if table name is tbabcdef).
+ The 5 letters are the first 5 letters of the table name.
+ If the table name has less than 5 letters, it completes it with underscores (example: tby__01234.unl, if table name is tby)
I would like to understand what is the meaning of the 5 numbers. Is there a way to guarantee that the list is alphabetically generated?

Answer 1

The 5 digits number used on the unload file is the tabid of the table.
I don't believe there is a way to guarantee that the list is alphabetically generated.
The dbexport and dbimport utilities
To get the tabid of a table query the systables system catalog table:
SELECT tabname, tabid
FROM systables
WHERE tabname = '<TABNAME>';
For a given list:
SELECT tabname, tabid
FROM systables
WHERE tabname IN (
'<TABNAME1>',
'<TABNAME2>',
'<TABNAME3>',
...
)
ORDER BY tabid;
For all user tables:
SELECT tabname, tabid
FROM systables
WHERE tabid > 99
AND tabtype = 'T'
ORDER BY tabid;
Needless to say you can reverse search by tabid:
SELECT tabname, tabid
FROM systables
WHERE tabid = '<TABNAME>';
SELECT tabname, tabid
FROM systables
WHERE tabid IN (
101,
102,
103,
...
)
ORDER BY tabid;
One way of mapping is:
SELECT tabname,
tabid,
RPAD(SUBSTR(tabname,0, 5), 5, '_')||tabid||'.unl' AS unl_file,
FROM systables
WHERE tabid > 99
AND tabtype = 'T'
ORDER BY tabid;
For the question if this is a good approach, it depends on some questions:
How many tables the source database has?
How many tables you intend to migrate?
The process should account for relations between tables and data (PK/FK/Triggers/...).
Remember the storage clause mentions the dbspaces when using the ss option.
...
For example, if you have a database with 1000 tables and just want 10, then it is easier to extract the schema from dbschema and then perform an unload of the data.
Here is a link of the list of Data migration utilities that comes with the engine.