When positioning only a few record blocks manually, results can be unpredictable.
When using LOCATE statements, it is easiest to control the layout of the data structure diagram if you use CA IDMS Schema Mapper in a fully manual mode, writing LOCATE statements for all of the record blocks in the diagram.
When you use LOCATE to position only a few key record blocks, the interaction between your LOCATE statements and CA IDMS Schema Mapper's automatic placement of the remaining record blocks can create an unexpected layout. CA IDMS Schema Mapper maintains the relative positions of record blocks you LOCATE, but it also inserts record blocks into empty space created by your LOCATE statements (depending on the size of the space created). CA IDMS Schema Mapper does this regardless of whether the OPTIONS COMPRESS parameter is on or off (see following discussion on use of COMPRESS parameter).
If you use LOCATE statements and do not manually LOCATE every record block in the diagram, you probably need to execute CA IDMS Schema Mapper several times to get the desired layout.
Using the OPTIONS COMPRESS parameter while working on the layout of a diagram.
If you will be executing CA IDMS Schema Mapper several times to obtain the desired layout of a diagram, you may want to turn off the OPTIONS COMPRESS parameter until the diagram nears completion.
When the COMPRESS parameter is off, CA IDMS Schema Mapper does not compress unused space from the diagram. CA IDMS Schema Mapper continues to insert record blocks into any empty space that it can.
When CA IDMS Schema Mapper creates the Transfer File and the COMPRESS parameter is on, CA IDMS Schema Mapper may rewrite some of the LOCATE statements you entered, changing the displacement values (the number of record blocks UP/DOWN/LEFT/RIGHT). CA IDMS Schema Mapper always maintains the relative positions of record blocks you LOCATE, but, with COMPRESS on, it may change the distances between some of the record blocks.
With the COMPRESS parameter off, CA IDMS Schema Mapper does not rewrite any of the LOCATE statements you entered as input. In other words, your LOCATE statements always appear unchanged in the Transfer File when you execute CA IDMS Schema Mapper with the COMPRESS parameter off. This can be an aid when you are working on the layout of the record blocks in a diagram.
Once you have the layout of the diagram near completion, you can turn on the COMPRESS parameter. CA IDMS Schema Mapper may rewrite any number of your LOCATE statements when it creates the Transfer File. CA IDMS Schema Mapper compresses any unused space after all record blocks have been LOCATEd in the diagram.
The size of an indexed record is larger than a record without indexes
An indexed record takes up more space on the diagram than a record without indexes. Because an index is represented by a diagonal line that projects from a corner of a record block, the record block is farther away from another record block allowing room for the indexes to be displayed.
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