Dynamic attribute modification

An option of the MFS Language utility allows an IMS application program to dynamically modify, replace, or simulate the attributes of a device field.

This dynamic attribute modification is requested in an output message definition by specifying ATTR=YES in an MFLD statement. MFS then reserves the first two data bytes of the output message field for attribute definition. Errors detected in the data of the 2-byte specification or X'3F' in the first or second attribute byte produce the results shown in the table below.

Attributes are always sent, even if no data is sent.

When dynamic attribute modification is specified for a device field with predefined attributes, an attribute is sent to the device for that field in every output operation, even if the data for this device field is not included in the output message. These attributes are used:

  • If the output message field has an attribute and the attribute is valid, then the dynamic attribute modification is performed.
  • If the message field is not included in the LPAGE being used or the attribute is not valid, the predefined attribute for the device field is used.

When attribute simulation is defined, the first byte of the device field is reserved for attribute data. The following attributes can be simulated:

  • Cursor position (3604 display only)
  • Nondisplayable
  • High-intensity displayable
  • Modified attributes

The two attribute bytes are defined in the following table.

Table 1. Definitions of the two attribute bytes
Byte Bit Definition
0 0-1 If both bits are on, requests that the cursor be placed on the first position of this field on the device. The first cursor-positioning request encountered in an LPAGE series (first MFLD with cursor attribute or cursor line/column value) that applies to a physical page is honored; these bits must be 00 or 11.
  2-7 Must be off.
1 0 Must be on.
  1
  1. If on, these attribute specifications are to replace the attribute byte defined for the field.
  2. If off, these attribute specifications are to be added to the attribute byte defined for the field logical OR operation. A zero in a bit position indicates that the defined attribute is to be used (that is, if bit 2 is 0 then the field will be protected or unprotected depending on the DFLD definition. A 1 in a bit position indicates that the corresponding attribute is to be used (that is, if bit 3 is 1 then the field will have the numeric attribute.)
  2 Protected
  3 Numeric
  4 High-intensity (forces detectable and displayable); if simulated, an * appears in the first byte of the device field.
  5 Nondisplayable (forces nondetectable); if simulated, no data is sent regardless of other attributes.
  6 Detectable (forces normal intensity).
  7 Premodified; if simulated, an underscore (_) appears in the first byte of the device field.
Notes:
  1. Bits 4, 5, and 6 are incompatible. If more than one is set, bit 4 takes precedence over bits 5 and 6. Bit 5 takes precedence over bit 6.
  2. If both bits 4 and 7 are simulated, an ! appears in the first byte of the device field.

Dynamic modification of attributes to detectable requires other action by the IMS application program to make the device function properly. Detectable fields must have a designator character and certain padding characters.

For DPM, field attribute information can be passed from the IMS application program to the remote program, but cannot be specified, unless ATTR=(YES,nn) appears in the MFS DFLD definitions.

See the appropriate component description manual to determine which extended attributes are available to a given terminal type.