Spooler Programmer's Guide

Using the Spooler Interface Procedures

Spooler Programmer’s Guide—522287-002

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Spooling—Level 3

An application process spooling at level 3 writes data to the collector using the spooler

interface procedures. SPOOLWRITE, SPOOLCONTROL, SPOOLCONTROLBUF, and

SPOOLSETMODE do not actually write a line of data to the collector each time one of

them is called. Instead, they put the data in the level-3-buffer you specified in an

earlier call to SPOOLSTART.

At the point that data specified in a call to a SPOOLWRITE, SPOOLCONTROL,

SPOOLCONTROLBUF, or SPOOLSETMODE procedure would cause the level-3-

buffer to overflow, the procedure checks to see whether bit 11 of the SPOOLSTART

flags parameter has been set to 1. If that bit is 0, the procedure writes the buffer to

the collector and begins refilling the buffer with the data line that would have

overflowed the buffer.

If bit 11 of flags is 1, however, the procedure exits before writing the level-3-

buffer to the collector and returns a spooler error code value of %11000. This

indicates to the application process that the level-3-buffer is about to be written to

the collector and that a checkpoint should be performed.

After checkpointing, you must use the same data again to call the procedure that

returned the %11000. This time, that procedure writes the buffer to the collector and

begins refilling the buffer with the data line.

When using the spooler interface procedures, you can perform spooling from a

NonStop process pair with or without checkpointing. In fact, you do not even have to

use the fault-tolerant bit in SPOOLSTART (bit 11 of the flags parameter), but this

would lead to inefficient checkpointing. Only fault-tolerant programs that use bit 11 of

flags are considered. The application must checkpoint the data stack, the lbuffer, the

latest line of data to be written, and the synchronization block of the file to the collector.

Figure 2-1 shows a flow chart of SPOOLWRITE, SPOOLSETMODE,

SPOOLCONTROL, and SPOOLCONTROLBUF procedures for handling a call that

would overflow the level-3-buffer.