First, a few minor criticisms.
a - Most of your questions can be answered easily by reading the Statements manual.
b - This forum - Natural Code Samples - is where you offer examples and techniques. Questions should be posted in the “Natural on Mainframes” or “Natural on Open Systems” forums.
c - You haven’t stated your platform. I’ll assume it is mainframe.
As to your questions:
1 - ESCAPE TOP with or without REPOSITION
ESCAPE TOP can be used in any of Natural’s looping statements to return to the top of the loop. ESCAPE TOP REPOSITION can be used only in a READ loop in which you have coded WITH REPOSITION. REPOSITION allows you to change the FROM value of the READ.
2 - ESCAPE BOTTOM with or without IMMEDIATE
ESCAPE BOTTOM is used to leave a loop; if an AT END OF DATA block is present, it is executed. ESCAPE BOTTOM IMMEDIATE is used to leave a loop, but ignores the AT END OF DATA block. The IMMEDIATE clause is redundant if no AT END OF DATA block is present.
3 - WRITE WORK with or without VARIABLE or RECORD
WRITE WORK does not have a RECORD clause.
For each WRITE WORK statement, Natural computes the logical record length, based on the field list. If more than one WRITE WORK statement exists for the same file, Natural compares the record lengths. If they do not match, the compiler issues an error message. If the records are intended to be fixed length, you must correct the WRITE WORK statements so that the lengths match. If the records are intended to be variable length, then code the VARIABLE keyword on each WRITE WORK statement.
4 - READ with and without MULTI-FETCH
In a READ loop, Natural issues a READ command to Adabas for each iteration of that loop. Performance can be improved by coding the MULTI-FETCH clause which causes Natural to request Adabas to return multiple records in a single call. Natural then replaces physical Adabas calls with accesses to the buffer of returned records.
If used improperly, Multi-fetch can drastically degrade performance. Multi-fetch should be used carefully and selectively.
Talk to a senior Natural developer in your shop for recommendations of how Multi-fetch works, when to use it, and how best to use it. This type of forum can’t do justice to such a complicated topic. Or have your organization contact Software AG (or one of the third-party instructors on these forums, such as yours truly) to arrange a training or mentoring session that includes multi-fetch.