Row formats for edit and validation routines

In writing an edit or validation routine, you must be aware of the format in which Db2 stores the rows of tables.

Column boundaries for edit and validation procedures
Db2 stores columns contiguously, regardless of word boundaries in physical storage, except LOB and XML columns. LOB or XML values are not stored contiguously; an indicator column is stored in a base table in place of the LOB or XML values.
Null values for edit procedures, field procedures, and validation routines
If null values are allowed for a column, an extra byte is stored before the actual column value.
Fixed-length rows for edit and validation routines
If all columns in a table are of fixed length, the rows are stored in fixed-length format. The rows are byte strings.
Varying-length rows for edit and validation routines
The rows of a table with varying-length columns are varying-length rows if they contain varying-length values. In basic row format, each varying-length value has a 2-byte length field in front of it. Those 2 bytes are not included in the column length attribute.
Varying-length rows with nulls for edit and validation routines
A varying-length column can allow null values. In basic row format, the value in the length field includes the length of the null indicator byte but does not include the length field itself.
EDITPROCs and VALIDPROCs for handling basic and reordered row formats
You can check the row format type (RFMTTYPE) to ensure that edit procedures (EDITPROC) and validation procedures (VALIDPROC) produce predictable results.
Converting basic row format table spaces with edit and validation routines to reordered row format
You cannot convert the table spaces with edit and validation routines from basic row format to reordered row format directly. You must perform additional tasks to convert these table spaces.
Dates, times, and timestamps for edit and validation routines
The values in columns with data types of DATE, TIME, and TIMESTAMP are stored in specific formats.
Parameter list for row format descriptions
Db2 passes a description of the row format to an edit routine or a validation routine through a parameter list, which is generated by macro DSNDROW. The description includes both the general row characteristics and the characteristics of each column.
Db2 decoding for numeric data in edit and validation routines
Db2 stores numeric data in a specially encoded Db2-coded format.

Parent topic: Exit routines