Updated February 2022; see History
ISMDMP fspec {/switches}
ISMDMP displays information about and/or dumps an ISAM index.
Parameters
fspec
the name of the index you wish to display. On execution, you will be offered the following choices for output of the information:
|
Option |
Description |
|
TTY |
Output to screen, starting with header |
|
DDT |
Output to screen, prompt for options on each block |
|
<filespec> |
Dump entire file in index order to the specified disk file |
switches
|
Switch |
Description |
|
/D |
Display and input block numbers in decimal instead of octal/hex |
|
/V |
Verbose mode. Displays additional details, assumes TTY output. |
|
/? |
Writes switch listing and usage info to the screen. |
The verbose option (/V) scans the IDX file to get actual counts of the index blocks in use by level, instead of just estimating it as in previous versions of ISMDMP. To keep the scan time reasonable and focused on the most important top levels, the scan will terminate when it reaches a level which is known—from scanning the level above it—to contain more than 5000 blocks, or when twenty seconds have elapsed. You can also hit any key to terminate the scan. Regardless of how the scan is terminated, the remaining levels will be estimated, as before. Note that since it is inefficient for the top level to contain more than one or two blocks, use of this feature can help you identify files that would benefit from restructuring, either increasing the index block size or the number of levels.
ISMDMP also indicates if the IDX was built using features that require a certain version of A-Shell, e.g.:
.ISMDMP TEST/V
Size of data record: 16
Size of dir entry: 14
Size of dir block: 1024
Size of key: 10
Type of key: 200 (requires A-Shell 5.1.1122+)
Entries per dir block: 72
Index levels: 4
Count by level: 1,3,198,14223
etc.
See Also
History
2022 February, A-Shell 6.5.1711: ISAM 1.X enhancement: IDX rock now contains a count of the keys allocated (additions minus deletions) along with the records allocated. This may be useful as a quick way to compare the number of keys with the number of records. Typically these should be the same, except in cases where the application deliberately adds more or less than one key to the IDX per record. Note that the keys allocated value will only be valid for files that have been rebuilt under A-Shell 6.5.1711+.
2022 February, A-Shell 6.5.1711, ISMDMP.LIT 2.0(145): Display new "Keys allocated" count if A-Shell version 6.5.1711+ and non-zero.
2013 March, A-Shell 1346, ISMDMP.LIT 2.0(140): Change verbose mode operation from estimating to scanning.