C-Library File IO Routines

PVSetEnvMode( )

Set Environment Variables

Format

intptr_t APIDEF PVSetEnvMode(HPVKENV hEnv, int iFlag, intptr_t iValue);

Where:

hEnv

Handle to environment structure

iFlag

Selector of the environment variable to be modified

Can be one of the following constants:

PV_BURST_MODE	1
PV_DIRTY_READ	2
PV_LOCK_MODE	3
PV_READ_ONLY	4
PV_MAX_MB	5

iValue

Corresponding value for iFlag:

PVK_BURST_ON	1
PVK_BURST_OFF	0
PVK_DIRTY_ON	1
PVK_DIRTY_OFF	0
PVK_DONT_CHECK_LOCK	1 (Don't check, never lock read records)
PVK_CHECK_LOCK	2 (Check for extracted records)
PVK_CHECK_LOCK_NOWAIT	4 (Check for extracted records, exit if locked)
PVK_HDR_LOCK_NOWAIT	8 (Don't wait for a locked header)
PVK_READONLY_ON	1
PVK_READONLY_OFF	0
PV_MAX_MB	(Maximum size of file segment in MB, integer value 0 to 2000)

Description

PVK_SetEnvMode( ) is used to set the value of environment variables. If successful, the function returns the previous value of the modified environment variable.

If specified and iValue is not valid, ERR_BAD_TYPE(-5) is returned. Returns PV_ERROR(-1) on failure.

Additional Notes

PV_BURST_MODE

Normal processing of a file involves locking each area of the file as it is read. Activating burst mode greatly reduces the number of locks issued against a file. With Burst mode set, the PXPIO routines lock the file header for either 50 file operations or three-tenths of a second, whichever occurs first. This decreases the number of times the file must be locked and the number of times that internal buffers may need to be reloaded.

PV_DIRTY_READ

Dirty Read mode of operation skips the normal file consistency checks. Dirty reads can speed file processing by reducing the number of locks issued against a file. However, this may result in inconsistent data should the file be updated while being read by the PXPIO routines.

PV_LOCK_MODE

The Lock Mode is used to control whether to check for locked/extracted records when reading and writing. The default setting is to not check for locked records for backwards compatibility with older versions of the PXPIO routines.

Note:
This flag should normally be set to PVK_CHECK_LOCK when files are being updated concurrently by PxPlus and applications using the PXPIO routines. A setting of PVK_DONT_CHECK_LOCK will allow the PXPIO routines to read and write a record that is extracted in PxPlus. The remaining settings provide a quicker means of checking for a locked record or file header and will return immediately rather than retrying the lock.

PV_MAX_MB

The PV_MAX_MB setting is used to control the approximate size of a file in megabytes before additional segments are created. This setting is functionally equivalent to the 'MB' (mega-bytes) system parameter in PxPlus. Values for PV_MAX_MB must be in the range of 0 (zero) to two thousand (2000). The default is two thousand (2000). Specifying a value of 0 (zero) resets this parameter to its default.