Enabling DECdtm Services

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HP OpenVMS System Manager's Manual, Volume 2:...

Managing DECdtm Services

Disabling DECdtm Services

Using the XA Gateway (Alpha and I64)

Enabling DECdtm Services

Enable DECdtm services only if you have previously disabled them and you now want to run software that uses DECdtm services.

How to Perform This Task

Deassign the logical name SYS$DECDTM_INHIBIT:
```
$ DEASSIGN/SYSTEM/EXECUTIVE_MODE SYS$DECDTM_INHIBIT
```
In an OpenVMS Cluster, use SYSMAN to deassign SYS$DECDTM_INHIBIT clusterwide.

Start up the DECdtm services process, TP_SERVER:
```
$ @SYS$STARTUP:DECDTM$STARTUP.COM
```
In an OpenVMS Cluster, use SYSMAN to start up the TP_SERVER process clusterwide.

Edit the SYS$MANAGER:SYLOGICALS.COM command procedure to delete the SYS$DECDTM_INHIBIT definition. This ensures that DECdtm services start automatically when you boot the system.

Example

This example shows how to enable DECdtm services in a cluster environment.

Deassign SYS$DECDTM_INHIBIT, then start up the TP_SERVER process.

$ RUN SYS$SYSTEM:SYSMAN
SYSMAN> SET ENVIRONMENT/CLUSTER
SYSMAN> DO DEASSIGN/SYSTEM/EXECUTIVE_MODE SYS$DECDTM_INHIBIT
SYSMAN> DO @SYS$STARTUP.DECDTM$STARTUP.COM
SYSMAN> EXIT

Edit the SYS$MANAGER:SYLOGICALS.COM command procedure to delete the SYS$DECDTM_INHIBIT definition.

Restrictions

DECdtm induces a system critical failure (BUGCHECK), which leads to a crash, when it does not have the operating environment it requires to perform its tasks. A typical example is the failure to allocate virtual memory. Such errors are treated as serious exceptions to DECdtm and hence fail with a BUGCHECK, which eventually crashes the system.

DECdtm depends mainly on its data structures to maintain the integrity and consistency of its transactions. Hence, any error or fatal condition during its execution is treated as a serious discrepancy; therefore, DECdtm raises a fatal exception and crashes the system.

HP recommends that you ensure that the operating environment has sufficient buffer in its system resources such as virtual memory and non-paged pool. If the crash occurs in an environment where DECdtm is not used, HP recommends that you prevent DECdtm from starting up. (To prevent DECdtm from starting up, refer to the section Disabling DECdtm Services.)

Defining a DECdtm Logical to Handle "Insufficient Dynamic Memory" on I64 Platforms

A DECdtm logical is provided to handle insufficient dynamic memory that occurs during the allocation of memory for the KPB (Kernel Process Block). The design logic is called Retry Logic; it allows users to define the system table logical name SYS$DECDTM_KPBALLOC_RETRYCNT to configure for the number of times (the Retry Count) the call to the system service EXE$KP_ALLOCATE_KPB is to be repeated when the return code is SS$_INSFMEM.

The system logical SYS$DECDTM_KPBALLOC_RETRYCNT is equated to the option string literal "MIN", "DEF", or "MAX." The string literals indicate a retry count of MIN=25, DEF=50, and MAX=100.

If the logical name SYS$DECDTM_KPBALLOC_RETRYCNT is not found in the system table, then the default count of DEF=50 is used for the Retry Logic.

Example:

$ DEFINE/SYS/EXEC SYS$DECDTM_KPBALLOC_RETRYCNT MAX

Disabling DECdtm Services

Using the XA Gateway (Alpha and I64)