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Process-Private Globals

Process-Private Globals

A process-private global is a variable that is only accessible by the process that created it. When the process ends, all of its process-private globals are deleted.

  • Process-specific: a process-private global can only be accessed by the process that created it, and it ceases to exist when the process completes. This is similar to local variables.

  • Always public: a process-private global is always a public variable. This is similar to global variables.

  • Namespace-independent: a process-private global is accessible from all namespaces.

  • Unaffected by argumentless KILL, NEW, WRITE, or ZWRITE. A process-private global can be specified as an argument to KILL, WRITE, or ZWRITE. This is similar to global variables.

Process-private globals are intended to be used for large data values. They can serve, in many cases, as a replacement for the use of the Mgr/Temp directory, providing automatic cleanup at process termination.

Naming Conventions

A process-private global name takes one of the following forms:


These four prefix forms are equivalent, and all four refer to the same process-private global. The first form (^||name) is the most common, and the one recommended for new code. The second, third, and fourth forms are provided for compatibility with existing code that defines globals.

Apart from the prefix, process-private globals use the same naming conventions as regular globals, as given in Rules and Guidelines for Identifiers. Briefly:

  • The first character (after the second vertical bar) must be either a letter or the percent (%) character.

    Process-private variable names starting with % are known as “percent variables” and have different scoping rules. In your code, for these variables, start the name with %Z or %z; other names are reserved for system use. For example: ^||%zmyvar.

  • Unlike local variables, no global name (including process-private globals) can contain Unicode letters — letter characters above ASCII 255. Attempting to include a Unicode letter in a process-private global name results in a <WIDE CHAR> error.

  • All variable names are case-sensitive, and this includes process-private global names.

  • A process-private global name must be unique within its process.

  • Unlike local variables, process-private global names are limited to 31 characters, exclusive of the prefix characters. You may specify a name longer than 31 characters, but only the first 31 characters are used. Therefore, a process-private global name must be unique within its first 31 characters.

  • Like other variables, process-private globals can take subscripts. See Rules About Subscripts.

Listing Process-Private Globals

You can use the ^$||GLOBAL() syntax form of ^$GLOBAL() to return information about process-private globals belonging to the current process.

You can use the ^GETPPGINFO routine to display the names of all current process-private globals and their space allocation, in blocks. ^GETPPGINFO does not list the subscripts or values for process-private globals. You can display process-private globals for a specific process by specifying its process Id (pid), or for all processes by specifying the "*" wildcard string. You must be in the %SYS namespace to invoke ^GETPPGINFO.

The following example uses ^GETPPGINFO to list the process-private globals for all current processes:

  SET ^||flintstones(1)="Fred"
  SET ^||flintstones(2)="Wilma"

The ^GETPPGINFO routine takes arguments as follows:

 do ^GETPPGINFO("pdf","options","outfile")

These arguments are as follows:

  • pdf can be a process Id or the * wildcard.

  • options can be a string containing any combination of the following characters:

    • b (return values in bytes)

    • Mnn (list only processes with process-private globals that use nn or more blocks)

      Use M0 to include processes without any process-private globals in the listing.

      Use M1 to exclude processes without any process-private globals from the listing, but include processes having only a global directory block. (This is the default.)

      Use M2 to exclude processes without any process-private globals from the listing, as well as those having only a global directory block.

    • S (suppress screen display; used with outfile)

    • T (display process totals only).

  • outfile is the file path for a file in CSV (comma-separated values) format that will be used to receive ^GETPPGINFO output.

The following example writes process-private globals to an output file named ppgout. The S option suppresses screen display; the M500 option limits output to only processes with process-private globals that use 500 or more blocks:

  DO ^GETPPGINFO("*","SM500","/home/myspace/ppgout") 
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