Re: Chunkname size limitations

The limitation for chunk names in version 7.X is 128 bytes (including the null) and with versions that have the new long identifier feature the limitation is increased to 256 bytes. Hope this helps, ---jmiller John Miller Art S. Kagel wrote: > Tom Smith wrote: > > > > Is there a limitation, practical or otherwise, on the size of a > > chunkname? Recommendations? We are using cooked files. > > Version? ODS 5.xx and 6.xx only permitted one disk page for the chunk > table this limited one to at most 64 chunks in theory if your > chunknames were 3 bytes long (ie /c1, /c2, /c3, etc) and actually > onspaces would never let you add the last chunk even if it fit on the > page because it miscalculated the amount of free space on the page. > For more reasonable chunknames (I used to use /i/ix01 leaving the 8th > char for the null else the null takes up an additional 4 bytes not one) > you can get about 56 chunks on a page with 4-7 byte names, 50 with 8-11 > byte names, etc (formula: (2020 / (32 + TRUNC((namelen + 4)/4)*4) - 1). > > In IDS 7.xx, 8.xx, 9.xx versions that initial chunk table page chains > to an additional block of 14 pages if the first page fills which would > allow over 700 chunks and the manual states that the engine supports > up to 1024 chunks which would require that additional chaining is > supported so there does not seem to be any practical limit. Of course > UNIX limits pathnames to 1024 characters so have fun. > > Personally I still use the convention of having a /i link to > $INFORMIXDIR/disks and keep the chunk links there keeping their names > under 15 characters (making them 1 byte less than a 4 byte word saves > 4 bytes in the chunk table). > > Art S. Kagel