Oracle Database Discussions

Hi,

I'm trying to understand the above error. It occurs when we are migrating data from one oracle database to another:

Error report:
SQL Error: ORA-12899: value too large for column "USER_XYZ"."TAB_XYZ"."COL_XYZ" (actual: 10, maximum: 8)
12899. 00000 - "value too large for column %s (actual: %s, maximum: %s)"
*Cause: An attempt was made to insert or update a column with a value
which is too wide for the width of the destination column.
The name of the column is given, along with the actual width
of the value, and the maximum allowed width of the column.
Note that widths are reported in characters if character length
semantics are in effect for the column, otherwise widths are
reported in bytes.
*Action: Examine the SQL statement for correctness. Check source
and destination column data types.
Either make the destination column wider, or use a subset
of the source column (i.e. use substring).


The source database runs - Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
The target database runs - Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production

The source and target table are identical and the column definitions are exactly the same. The column we get the error on is of CHAR(8). To migrate the data we use either a dblink or oracle datapump, both result in the same error. The data in the column is a fixed length string of 8 characters.

To resolve the error the column "COL_XYZ" gets widened by:
alter table TAB_XYZ modify (COL_XYZ varchar2(10));
-alter table TAB_XYZ succeeded.

We now move the data from the source into the target table without problem and then run:
select max(length(COL_XYZ)) from TAB_XYZ;
-8

So the maximal string length for this column is 8 characters. To reduce the column width back to its original 8, we then run:
alter table TAB_XYZ modify (COL_XYZ varchar2(8));
-Error report:
SQL Error: ORA-01441: cannot decrease column length because some value is too big
01441. 00000 - "cannot decrease column length because some value is too big"
*Cause:
*Action:

So we leave the column width at 10, but the curious thing is - once we have the data in the target table, we can then truncate the same table at source (ie. get rid of all the data) and move the data back in the original table (with COL_XYZ set at CHAR(8)) - without any issue.

My guess the error has something to do with the storage on the target database, but I would like to understand why. If anybody has an idea or suggestion what to look for - much appreciated.

Cheers.