PMDF System Manager's Guide

This section lists options relating to message size, such as limits on the size of messages allowed in PMDF, message size affecting message processing priority, limits on the extent to which PMDF looks into messages of complex MIME structure, and fine tuning of message fragmentation.

BLOCK_LIMIT (integer > 0)

This option places an absolute limit on the size, in blocks, of any message which can be sent or received with PMDF. Any message exceeding this size will be rejected. By default, PMDF imposes no size limits. Note also that the blocklimit channel keyword can be used to impose limits on a per-channel basis. The size in bytes of a block is specified with the BLOCK_SIZE option.

BLOCK_SIZE (integer > 0)

PMDF uses the concept of a "block" in several ways. For example, the PMDF log files (resulting from placing the logging keyword on channels) record message sizes in terms of blocks. Message size limits specified via the maxblocks keyword are also in terms of blocks. Normally a PMDF block is equivalent to 1024 characters. This option can be used to modify this sense of what a block is. A good alternative might be 512, to match the OpenVMS definition of a block.

Note PMDF stores message sizes internally as an integer number of blocks. If the size of a block in bytes is set to a very small value it is possible for a very large message to cause an integer overflow. A message size of greater than 2**31 blocks would be needed, but this value is not inconceivable if the block size is small enough.

BOUNCE_BLOCK_LIMIT (integer)

This option can be used to force bounces of messages over the specified size to return only the message headers, rather than the full message content.

CONTENT_RETURN_BLOCK_LIMIT (integer)

This option can be used to force on the NOTARY non-return of content flag for messages over the specified size; if such a message is subsequently bounced by a system that supports NOTARY, then the original message contents will not be included in the bounce message.

LINE_LIMIT (integer)

This option places an absolute limit on the overall number of lines in any message which can be sent or received with PMDF. Any message exceeding this limit will be rejected. By default, PMDF imposes no line count limits. Note also that the linelimit channel keyword can be used to impose limits on a per-channel basis.

MAX_HEADER_BLOCK_USE (real number between 0 and 1)

The MAX_HEADER_BLOCK_USE keyword controls what fraction of the available message blocks can be used by message headers. See Section 2.3.4.77 for additional information on how this option interacts with the maxblocks channel keyword.

MAX_HEADER_LINE_USE (real number between 0 and 1)

The MAX_HEADER_LINE_USE keyword controls what fraction of the available message lines can be used by message headers. See Section 2.3.4.77 for additional information on how this option interacts with the maxlines channel keyword.

MAX_INTERNAL_BLOCKS (integer)

The MAX_INTERNAL_BLOCKS option specifies how large (in PMDF blocks) a message PMDF will keep entirely in memory; messages larger than this size will be written to temporary files. The default is 30. For systems with lots of memory, increasing this value can provide a performance improvement.

MAX_MIME_LEVELS (integer)

Specify the maximum depth to which PMDF should process MIME messages. The default is 100, meaning that PMDF will process up to one hundred levels of message nesting. Higher values can require additional amounts of memory and, for the Dispatcher, additional per-thread storage space; see the discussion of the STACKSIZE Dispatcher option in Section 11.3.1.

MAX_MIME_PARTS (integer)

Specify the maximum number of MIME parts which PMDF should process in a MIME message. The default value is 0, meaning no limit is imposed.

NORMAL_BLOCK_LIMIT (integer)

The NORMAL_BLOCK_LIMIT option can be used to instruct PMDF to downgrade the priority of messages based on size: messages above the specified size will be downgraded to non-urgent priority. This priority, in turn, can affect whether the message is processed immediately, or whether it is left to wait for processing until the next periodic job runs; see Section 2.3.4.9. The value is interpreted in terms of PMDF blocks, as specified by the BLOCK_SIZE option. Note also that the normalblocklimit channel keyword can be used to impose such downgrade thresholds on a per-channel basis. Section 2.3.4.10,

NON_URGENT_BLOCK_LIMIT (integer)

The NON_URGENT_BLOCK_LIMIT option can be used to instruct PMDF to downgrade the priority of messages based on size: messages above the specified size will be downgraded to lower than non-urgent priority, meaning that they will not be processed immediately and will wait for processing until the next periodic job runs; see Section 2.3.4.9. The value is interpreted in terms of PMDF blocks, as specified by the BLOCK_SIZE option. Note also that the nonurgentblocklimit channel keyword can be used to impose such downgrade thresholds on a per-channel basis.

URGENT_BLOCK_LIMIT (integer)

The URGENT_BLOCK_LIMIT option can be used to instruct PMDF to downgrade the priority of messages based on size: messages above the specified size will be downgraded to normal priority. This priority, in turn, can affect whether the message is processed immediately, or whether it is left to wait for processing until the next periodic job runs; see Section 2.3.4.9. The value is interpreted in terms of PMDF blocks, as specified by the BLOCK_SIZE option. Note also that the urgentblocklimit, channel keyword can be used to impose such downgrade thresholds on a per-channel basis.