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Changes the default block size of new memo field (.DBT) files.

Syntax

SET MBLOCK TO <expN>

<expN>

A number from 1 to 512 that sets the size of blocks used to store new memo (.DBT) files. (The actual size in bytes is the number you specify multiplied by 64.)

Default

The default value for SET MBLOCK is 8 (or 512 bytes). To change the default, update the MBLOCK setting in PLUS.ini. To do so, either use the SET command to specify the setting interactively, or enter the MBLOCK parameter directly in PLUS.ini.

Description

Use SET MBLOCK to change the size of blocks in which dBASE Plus stores new memo field (.DBT) files on disk. You can specify a block size from 64 bytes to approximately 32K. The MBLOCK setting overrides any previous block size defined by the SET BLOCKSIZE command or specified in the PLUS.ini file. After the block size has been changed, new memo .DBT files are created with the new block size. dBASE Plus stores data in each memo field in a group made up of as many blocks as needed.

After the block size is changed, memo fields created with the COPY, CREATE, and MODIFY STRUCTURE commands have the new block size. To change the block size of an existing memo field file, use the SET BLOCKSIZE command to change the block size and then copy the table containing the associated memo field to a new file. The new file then has the new block size.

When the block sizes are large and the memo contents are small, memo (.DBT) files contain unused space and become larger than necessary. If you expect the contents of the memo fields to occupy less than 512 bytes (the default size allocated), set the block size to a smaller size to reduce wasted space. If you expect to store larger pieces of information in memo fields, increase the size of the block.

SET MBLOCK is similar to the older SET BLOCKSIZE command except for two advantages:

You can allocate different block sizes for memo field and index data, whereas SET BLOCKSIZE requires the same block size for both. To allocate block sizes for index data, use SET IBLOCK.

You can specify smaller blocks with SET MBLOCK than with SET BLOCKSIZE. SET BLOCKSIZE creates blocks in increments of 512 bytes, compared to 64 bytes with SET MBLOCK.