Important: Any modification to boot block information is not supported by Apple.
The SystemStartup information (for a Macintosh system or a file server), is stored in logical blocks 0 and 1 of an HFS startup disk. It contains the maximum number of files that can be open simultaneously. This is currently set to 10. The location for this parameter is $7A of logical block 0 on an HFS disk. The number at $7A (default is $000A or Decimal 10) serves as the parameter for files open at one time.
The number $000A (or Decimal 10), for instance, is proper for 128K and 512K systems. If the Macintosh is equipped with 1MB or more of memory, the system multiplies the number at $7A by four (that is, it becomes decimal 40) and uses the new number as the new file limiter.
You can use a disk editor, like FEdit, to change this number. The File Control Block Buffer and System Heap size will be calculated with the changed files open parameter upon restarting.
If you must raise this number, do it in small increments. Raising the number in location $7A, as some users have done, can force the system to set aside too much memory. This causes a system error, which, because it is unexpected, the system cannot handle. The result is a system lockup.
Tech Note 113 also relates to the topic.
Note: FoxBase allows a maximum of 48 open files, regardless of how many the Macintosh OS allows.
The following Tech Info Library article can help you find the Tech Note mentioned here:
Article 24493: "
Apple Tech Notes: What They Are, Where To Find Them"