ALTDSEG

NM and CM callable.

Reduces the storage required by the extra data segment when moved into main memory and expands storage as required, allowing for a more efficient use of memory. Data segment management (DS) capability is required.




	NOTE: Data segment management (DS) intrinsics are not recommended for use in the operating system native mode programming environment; use of DS intrinsics degrade program performance.

Syntax

         U16V   I16V    I16

ALTDSEG(index,increment,size);

Parameters

index

16-bit unsigned integer by value (required)

Indicates the index of the extra data segment, obtained from the GETDSEG call.

increment

16-bit signed integer by value (required)

Specifies the value, in half words, the extra data segment is to be changed. A positive value requests an increase; a negative value requests a decrease.

size

16-bit signed integer by reference (required)

Returns the new size of the extra data segment after incrementing or decrementing has occurred.

Operation Notes

Incrementation and decrementation is accomplished in even multiples of four half words, which are rounded up. For example (in half words):

Present Segment Size	Change Value	New Segment Size
128	-3	128
128	-4	124
128	+1	132
128	+3	132
128	+4	132

When a data segment is created through GETDSEG, the required virtual space is allocated by the system to accommodate the original length of the data segment. This virtual space is allocated in increments of 512 half words. For example, creation of an extra data segment with a length of 600 half words results in the allocation of 1024 half words of virtual space.




	NOTE: `ALTDSEG` cannot increase the size of a data segment to exceed the virtual space originally allocated through `GETDSEG`.

When GETDSEG is called in privileged mode, the ALTDSEG intrinsic must also be called in privileged mode.

Condition Codes

CCE (2): Request granted.
CCG (0): Request granted. An illegal decrement was requested to a total segment size of <=0; the current size remains in affect. An illegal increment was requested for a total segment size greater than the virtual space originally assigned; the size of the virtual space is granted and returned to the size parameter.
CCL (1): Request denied. An illegal index parameter was specified.

Additional Discussion

Intrinsics: FREEDSEG, GETDSEG
Commands: None
Manuals: Introduction to MPE XL for MPE V Programmers (30367-90005)

ALTDSEG

Technical documentation

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Syntax

Parameters

Operation Notes

Condition Codes

Additional Discussion