Getting Started with DECTPU 2.4 Using Journal Files

2.4.3 Buffer-Change Journal File-Naming Algorithm

By default, DECTPU creates the buffer-change journal file name by using the following algorithm:

1.Converts all characters in the buffer name that are not alphanumeric, a dollar sign, underscore, or hyphen to underscores

2.Truncates the resulting file name to 39 characters

3.Adds the file type .TPU$JOURNAL

For example, a buffer named TEST.BAR has a default journal file name of TEST_

BAR.TPU$JOURNAL.

DECTPU puts all journal files in the directory defined by the logical name TPU$JOURNAL. By default, this logical is defined as SYS$SCRATCH. You can reassign this logical name. For example, if you want journal files written to the current default directory, define TPU$JOURNAL as [ ].

2.5 Avoiding Errors Related to Virtual Address Space

DECTPU manipulates data in a process’s virtual memory space. If the space required by the DECTPU images, data structures, and files in memory exceeds the virtual address space, DECTPU tries to write part of the data to the work file, thus freeing up space for other parts of the data that it needs immediately.

If the work file is full, DECTPU attempts to return either a TPU$_GETMEM or TPU$_NOCACHE error message. Although you may be able to free up some space by deleting unused buffers, Compaq recommends that you terminate the DECTPU session if you encounter either of these errors. You can then start a new session with fewer or smaller buffers. Alternatively, you may want to put the work file on a disk that contains more free space. Use one of the following methods to do this:

•Redefine TPU$WORK to point to the disk with more free space.

•Invoke DECTPU with the /WORK=filename qualifier.

DECTPU may be unable to signal an error when it frees up memory by writing to the work file. In this case, DECTPU aborts with a fatal internal error.

You may be able to avoid writing to the work file by increasing the virtual address space available to a process. The virtual address space is controlled by the following two factors:

•The SYSGEN parameter VIRTUALPAGECNT

•The page file quota of the account you are using

The VIRTUALPAGECNT parameter controls the number of virtual pages that can be mapped for a process. For more information on VIRTUALPAGECNT, see the description of this parameter in the OpenVMS documentation on the System Generation Utility (SYSGEN).

The page file quota controls the number of pages in the system paging file that can be allocated to your process. For more information on the page file quota, see the description of the /PGFLQUOTA qualifier in the OpenVMS documentation on the Authorize Utility (AUTHORIZE).

You may need to modify both the VIRTUALPAGECNT parameter and the page file quota to enlarge the virtual address space.

2–8Getting Started with DECTPU

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Compaq AA-PWCBD-TE manual Avoiding Errors Related to Virtual Address Space, Bar.Tpu$Journal
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