In general, DML statements are highly portable. SELECT, INSERT, UPDATE, and DELETE statements are similar across the IBM relational database products. Most applications primarily use DML SQL statements, which are supported by the DB2 Connect program and DRDA protocol.
When numeric data is transferred to DB2 Universal Database, the data type may change. Numeric and zoned decimal SQLTYPEs (supported by DB2 for AS/400) are converted to fixed (packed) decimal SQLTYPEs.
Mixed-byte data can consist of characters from an extended UNIX code (EUC) character set, a double-byte character set (DBCS) and a single-byte character set (SBCS) in the same column. On systems that store data in EBCDIC (OS/390, OS/400, VSE, and VM), shift-out and shift-in characters mark the start and end of double-byte data. On systems that store data in ASCII (such as OS/2 and UNIX), shift-in and shift-out characters are not required.
If your application transfers mixed-byte data from an ASCII system to an EBCDIC system, be sure to allow enough room for the shift characters. For each switch from SBCS to DBCS data, add 2 bytes to your data length. For better portability, use variable-length strings in applications that use mixed-byte data.
Long fields (strings longer than 254 characters) are handled differently on different systems. A DRDA server may support only a subset of scalar functions for long fields; for example, DB2 for MVS/ESA allows only the LENGTH and SUBSTR functions for long fields. Also, a DRDA server may require different handling for certain SQL statements; for example, DB2 for VSE & VM requires that with the INSERT statement, only a host variable, the SQLDA, or a NULL value be used.
The LOB data type is not supported by the DRDA architecture. DB2 Connect cannot send data with this data type.