Specifications & Features
Updated November 2018; see History
The following table lists various sizes, capacities and limits for ISAM-A files and processing. Note, however, that some of these limits have been arbitrarily set just for efficiency. If you have legitimate need for larger limits, contact us. Also note that where the word "extension" appears in the table below, this indicates a feature that was not present in the AMOS version and which may require some modification to your application; see A-Shell Extensions for more details.
Item |
Size / Limit / |
Updated in A-Shell |
|---|---|---|
Record size |
16K |
988 of Dec 07; 8K |
Number of keys per record |
20 |
|
DAT file size |
2 terabytes |
4.9.948; 2GB |
IDX file size |
2 terabytes (theoretical) |
5.1.1134; 2GB |
Records per file |
2 ^ 31 |
|
Bytes per key |
120 |
|
Parts (fields) per key |
20 |
|
Duplicate keys |
65536 |
|
Compressed keys |
yes (optional, extension) |
|
Compressed data records |
yes (optional, extension) |
|
Transaction support |
yes Linux, no Windows |
|
File recovery from log |
yes Linux, no Windows |
|
Audit trail |
maybe; under review |
|
Auto expansion of file |
yes |
|
Index rebuild utility |
yes |
|
Index verification utility |
yes |
|
Add/delete index without dump/reload |
yes |
|
ODBC / OLEDB / SQL access |
yes via third party utilities |
|
History
November 2018, A-Shell 6.5.1650: • Enable variable length records in the Windows version (matching Unix); • Increase the maximum number of key parts from 8 to 20, and the maximum key length from 80 to 120, in the Unix version (matching Windows). Note: the only outstanding difference between the two versions is that the Windows version doesn't support transaction logging. Also note: these changes update the ISAM-A version, as displayed by the ISMUTL header, to 6.11r.
