FNVMASK parameter
Filename version mask
Summary
- Default value
- X'00'
- Parameter type
- System
- Where set
- User 0 CCAIN parameters
- Related products
- Sirius Performance Enhancements V3
- Introduced
- Before Sirius Mods 6.7
Description
This is a single-byte bitmask parameter. If set to a non-zero value, FNVMASK indicates the bytes in filenames that are not required to match those in the filenames on the physical file pages. Bytes in filenames corresponding to the ON bits in FNVMASK do not have to match the comparable bytes in the physical filenames.
For example, if FNVMASK is set to X'10', the fourth byte of a filename does not have to match the physical filename. That is, you might be able to open a file with physical name FOOBAR as FOODAR, or FOOLAR, or FOOTAR. If FNVMASK were set to X'34', bytes 3, 4, and 5 wouldn't need to match, so FOOBAR could be opened as FOOLER, or FOCKER, or FOLDER, to name just a few.
FNVMASK facilitates sharing of data between Onlines, making it possible for two files with the same physical name to be opened in the same Online by opening them under two different names that differ only in the bytes indicated by FNVMASK. This can be especially useful in moving procedures from one file to a like-named file to be used in a different Online.
Note: FNVMASK in no way alters the file-enqueuing behavior of Model 204 — no file opened for update by one Online can be opened by another, regardless of the name under which it is opened.
Use of FNVMASK does not weaken page trailer validation, as page trailer validation at disk reads will validate the name against all bytes of the physical file name, regardless of FNVMASK.