The Initialization process of the NPAM

The Teradata Named Pipe Access Module (NPAM) provides an inter-process communication link between a writer process (such as FastExport) and a reader process (such as FastLoad). The NPAM can also be used by Teradata Parallel Transporter (TPT) for data transfer.

The reader process will initialize the NPAM module via an Initialization string and this article details the various parameters that are initialized during this process.

NPAM – Initialization string

The initialization string contains the sets of parameter keywords and their respective values (to be initialized with). The format of the Initialization string is as follows:

"keyword1=value1 keyword2=value2 keyword3=value3 ..."

keyword identifies the initialization parameters

value is either an integer or a string, sometimes enclosed in single or double quote characters

The Initialization string is used in the Teradata Client utility job script to specify or override the default values of the parameters. The Initialization string can contain the values of the parameters listed below.

block_size
confirm_fallback_deletion
fallback_directory
fallback_file
log_directory
log_level
need_full_block
pipe_wait
signature_check

The NPAM parses the Initialization string, validates and sets the parameters with their respective values (specified in the Initialization string).

Example illustrating the Initialization string

The NPAM can be initialized using the following statement in the TPUMP job script. Please note that the string displayed within the single quotes 'log_level= ... ' is the initialization string.

.IMPORT

INFILE np_one   /* “np_one” is the name of the Named pipe */

LAYOUT LAY1A    /* LAY1A is the data layout name */

APPLY LABELA    /* LABELA is the label name */

FORMAT TEXT     /* TEXT is the data format type */

axsmod np_axsmod.so 'log_level=5 log_directory=. buffer_size=6500 fallback_directory=.
fallback_file=test.fbf confirm_fallback_deletion=y need_full_block=n pipe_wait=320 signature_check=2';

The following table details the purpose and significance of each parameter used in the Initialization string.

Parameter	Usage	Description
`block_size`	`block_size=n` or b=n	Block size (in bytes) of the data transfer operation where `n` is an integer from `1` to `2147483647`. The default value of the `block_size` parameter is `65536` bytes.
`confirm_fallback_deletion`	`confirm_fallback_deletion=y` or `cfd=y`	The values can be either '`y`', '`n`', '`yes`' or '`no`'. This flag informs the NPAM whether to present a confirmation prompt before deleting the fallback data file. The default value of `confirm_fallback_deletion` is ‘`no`’.
`fallback_directory`	`fallback_directory=directorypath` or `fd=directorypath`	Path of the fallback data file directory. The default directory of the fallback_directory parameter is: `/opt/np_axsmod` on UNIX systems `%TEMP%` or `%WINDIR%\temp` on Windows systems
`fallback_file`	`fallback_file=filename` or `ff=filename`	Name of the fallback data file.
`log_directory`	`log_directory=directorypath` or `ld=directorypath`	Path of the log file directory. The default directory of the `log_directory` parameter is: `/tmp` on UNIX systems `%TEMP%` or `C:\` on Windows systems
`log_level`	`log_level=n` or `ll=n`	The values can be `0`, `1`, `2`, `3`, `4`, `5` or `6`. The default value of `log_level` is ‘`0`’. The significance of each value and the level of details to be posted to the log file is presented below: “0” : Indicates Disable. Disables the log operation. This is the default `log_level` value of the `log_directory` path. “1” : Indicates Critical. Logs events where a critical resource, such as memory or its message strings cannot be obtained. “2” : Indicates Error. Logs error conditions. “3” : Indicates Warning. Logs unusual events that do not halt processing. “4” : Indicates Information. Logs operational events or statistics. “5” : Indicates Debug. Logs details normally required for debugging purpose. “6” : Indicates Trace. Logs all available information about each I/O operation.
`need_full_block`	`need_full_block=n` or `nfb=n`	The values can be either '`y`', '`n`', '`yes`' or '`no`'. Used to determine if a full data buffer block is required prior to returning to the calling process. The default value of `need_full_block` is ‘`yes`’.
`pipe_wait`	`pipe_wait=n` or `pw=n`	Holds the sleep interval (in milliseconds) for polling the pipe when `need_full_block=no`. By default, the `pipe_wait` is set to `10` milliseconds.
`signature_check`	`signature_check=checklevel` or `sc=checklevel`	The values can be `0`, `1` or `2`. Sets the signature check level. The default value of the signature_check is ‘`2`’. The significance of each value is presented below: “0” : Indicates Disabled. A signature is neither calculated nor checked. “1” : Indicates Enabled / No Return Calculates, checks the signature and logs a warning if the check fails. It does not return an error condition. “2” : Indicates Enabled / Return Calculates, checks the signature and logs an error if the check fails. It returns an error condition.

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NPAM – Initialization string

Example illustrating the Initialization string