You can also consider the FASTPATH option, which records execution counts in a different way. Where the PATH option uses eight bytes of storage for every instruction executed, FASTPATH uses only four, but allocates a contiguous block of storage to record information by assuming that the maximum number of instructions in your program is the program size divided by 2. Thus the FASTPATH option may, or may not, take more storage than the PATH option. However, it does not have to scan a list to find the instruction count information, so it executes in much less time.

The FASTPATH option is really a "mode" type of setting. The type of storage allocation and recording performed is determined by whether you issue a SET OPTION ON FASTPATH or a SET OPTION ON PATH command first. Once you have set the FASTPATH option to ON, you can use SET OPTION ON/OFF PATH to turn execution recording on and off; the allocation method does not change once it is initially set. Because the allocation mechanism assumes a given program size and start address, the SET BASE and SET SIZE commands may not be used after the FASTPATH option is set.

When using the FASTPATH option, instruction count information is only collected for the original target module. All other instructions executed are ignored.