DELTA PLAM Delta Storage

DELTA[1] Delta storage in PLAM librarys.

Delta storage means that different versions of the same element can be saved by only saving the differences to the preceding version. In contrast to a full save of the element, the delta technique achieves a significant reduction in the required storage space.

The Delta User Option achieves the following:

a) If the User Option DELTA, or DELTA Y is entered when selecting library elements, all available delta versions are displayed in the file list as an entry. Normally, i.e. if the DELTA User Option is not specified, or is specified in the form DELTA H, then only the highest version of an element is selected.

b) For each element version, the base version necessary for the Delta creation is displayed in the User Option column. Naturally the first version of an element has itself as a predecessor. The first version is flagged in the list with an asterisk (*).

DELTA: The base version is displayed according to the internal version counter (analogous to LMS with PAR TOC=D).

DELTA1: The last four digits of the actual version description of the base element is displayed.

c) If an element saved in Delta format is displayed in a file list, and is transfered to another PLAM library (where no element with this name exists) with a Variable Action ONXADD, then the element will be transfered in Delta format. Normally, i.e. without the Delta User Option, a delta-stored element will be transfered using ONXADD as a full element, so long as no element with this name exists in the target library.

Selection parameter: Y | H | N

Y Only elements of the PLAM library stored in Delta format will be selected. All versions of the element will be displayed in the file list.

H Only elements of the PLAM library stored in Delta format will be selected. Only the highest (current) version of each Delta element will be displayed in the file list.

N Only non-Delta format elements of the PLAM library will be selected.