Segment wait (SEGWT) macro instruction

The SEGWT macro is used to stop processing in the requesting segment until the requested segment is in virtual storage.

As a result of using any of the examples in Table 1, no further processing takes place until the requested segment and all segments in its path are loaded when not already in virtual storage. Processing resumes at the next sequential instruction in the requesting segment after the requested segment has been loaded.

Table 1. Use of the SEGWT macro instruction
Example	Name¹	Operation	Operand^{2, 3}
1	ADCON	SEGLD SEGWT L branch DC	external name external name Rn,ADCON V(name)
2		SEGWT L	external name Rn,=V(name)
Notes: When the name field is blank, specification of a name is optional. External name is an entry name or a control section name in the requested statement. Rn is any other register and is used to hold the return address. This register is usually register 14.

If the SEGWT and SEGLD macro instructions are used together, overlap occurs between processing and segment loading. Use of the SEGWT macro instruction serves as a check to see that the necessary information is in storage when it is finally needed (see Example 1 in Table 1). In Example 2 in Table 1, no overlap is provided. The SEGWT macro instruction initiates loading, and processing is stopped in the requesting segment until the requested segment is in virtual storage.

The external name specified in the SEGWT macro instruction must be defined with a 4-byte V-type address constant. The high-order bit is reserved for use by the control program and must not be altered during execution of the program.

If the contents of a virtual storage location in the requested segment are to be processed, the entry name of the location must be referred to by an A-type address constant.