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Resizing History Files

(changed server version 6.17f or later)

MOMI automatically creates history files when enabled. The following table lists the initial size of these files:

Two methods are available to re-size a history file.  

Alter maximum extents

The utility FUP may be used, while $MOMI is running, to alter the maximum extents of the history files.

To increase the amount of history disk space allowed, increase MAXEXTENTS of the history file(s).  

To decrease the amount of history disk space allowed, reduce the MAXEXTENTS of the history file(s). The file system will not allow a reduction in the maximum extents below the End of File (EOF).   

If the default amount of space consumed by history files (as shown above) is too large for the NonStop System, start MOMI, wait a few seconds to allow the files to automatically create, and then stop MOMI. In FUP "set like" a history file, purge the old file, adjust the MAXEXTENTS and/or primary/secondary extent sizes, then create a new file. MOMI must be able to allocate at least one extent on every file defined or an error will result.

See the screen Server_Info for information on how to alter the history files MAXEXTENTS from within the MOMI PC Client.

Load data into a larger file

Once a history file reaches the maximum number of extents allowed by the system, usually 978, storing additional history requires creation of a new file. Optionally, load data from the old file into the new file (if the old data is desired and you have time to wait for the load to complete).

Some math is required to determine the size of the new file, but a good starting point is its current size as reported by: FUP INFO <file-name>,detail. The value to the right of EOF is the number of bytes the file occupies. Take this number and perform the following math:

(eof / 2048) / 32 = ext-size          (use this result below)

This formula takes the file EOF in bytes, divides by the number of bytes per disk page (2048), and then divides that by the number of extents for the file to initially occupy (32). This last number is not much more than a good guess but if you are loading data from a file with many hundreds of extents the disk may not have one very large chunk of contiguous free space. So, instead of one computing for one large chunk of free disk space this formula tries for at least 32 smaller ones.

The following steps describe how to create a new file and then optionally load it with data. The values in green are dependent on which history file is being modified and your configuration needs. Substitute the HST01DB name (used in this example) with the desired file on the NonStop System:

1. Logon to a TACL prompt on the NonStop System with sufficient authority to stop & restart $MOMI plus access its files.

2. Stop $MOMI. Wait until all its processes have automatically stopped.

3. Volume to the location of existing MOMI files, starting with FUP execute the following sequence of commands -

FUP

RENAME HST01DB,HST01DB1

SET LIKE HST01DB1

SET FORMAT 2

SET EXT (ext-size,ext-size)

SET MAXEXTENTS 64                                                    (double current size)

CREATE HST01DB

LOAD HST01DB1,HST01DB,SORTED                          (optional)

EXIT

4. Restart MOMI. Check the EMS log to insure the new file was accepted (an error message is generated if a problem occurs).

5. At a later time, delete the old file.

Considerations:

a) absolutely, positively, and without a doubt insure that other applications on the system will not be impacted by the disk space consumed. Use the DSAP utility to confirm the availability of the extent size chosen. Remember that total free disk space does not indicate the availability of the extent size chosen.

b) depending on the file size and system performance, the LOAD command may take 45 minutes or more. One way to speed the process is to perform the LOAD from one disk volume to another disk volume then after the load completes FUP DUP the file back (if necessary). This may be faster than a LOAD when both the input & output are on the same volume.

Leave all other attributes of a MOMI file 'as is'. MOMI will not use the file if an expected attribute is changed. Check the EMS log immediately after restarting MOMI to insure that the converted history file is accepted (MOMI writes a message to the EMS log (i.e. $0) if the history file is not accepted). If this new file is not accepted fallback to the original.