Question:  How do I interpret the output of "SET MODE DIAGNOSTIC?"

Explanation:

Here's a fragment of MODE DIAGNOSTIC output and some explanation:

yes? SET MODE DIAGNOSTIC
yes? LOAD SST[l=1:400@AVE]
 getgrid EX#1   5 D: 2  I:    1    1  J:    1    1  K:    1    1  L:    1    1
 eval    EX#1   4 D: 2  I: -111 -111  J: -111 -111  K: -111 -111  L: -111 -111
 strip gathering SST on Y axis:     1    90
 strip -->; SST[T=01-JAN-1946:01-MAY-1979@AVE,D=2]
 reading SST    3 D: 2  I:    1  180  J:    1    4  K: -111 -111  L:    1  400
 doing -->; SST[T=01-JAN-1946:01-MAY-1979@AVE,D=2]
 doing gathering SST on Y axis:     1     4

Explanation:

• D: 2  tells us that the operations are from data set #2
• the getgrid pass determines the grid (coordinate system) of the result
• eval EX#1 is the start of evaluation for the first expression (there may be multiple comma-separated expressions)
• - I: -111 -111 means that the limits on the I (X) axis are IMPLIED (unknown). Explicit limits may improve performance and memory management.
• strip means that Ferret has detected the need for an operation and allocated space for it on a stack.
• strip gathering SST on Y axis means this calculation is being broken into slices along the Y axis (to fit into memory)
• reading SST ... means IO is in progress. The I,J,K,L limits are shown.  You may see delays during large IO operations.
• doing tells us the operation that was "stripped" above is being done
• gathering  SST on Y axis:  1  4 tells us that the J=1:4 slice of the calculation has been completed.  J=5:8 will probably follow.