HostBridge VSAM files can and should be treated as any other application files.  As such, they can be shared cross-region so long as all of the standard CICS precautions are taken.  HostBridge accesses all files using standard CICS APIs and relies on CICS to protect the integrity when files are shared cross-region.

By default, the HostBridge VSAM files are allocated with the SHAREOPTION (1,x), the most restrictive sharing option.  In older versions of HostBridge (pre release 6.5), the VSAM files were allocated with the least restrictive sharing option.  It was found that if users chose to share files across regions there were occurrences of data loss because writes were performed from multiple systems.

Below are a series of tables that lays out your options for the HostBridge VSAM files.  In all of the tables, FOA stands for File Operations Attributes (as defined in the CICS RDO entry for the file).

For files defined to one region only:

Access RequiredVSAM ShareoptionsFOA AddFOA BrowseFOA DeleteFOA ReadFOA Update
All Read / No Write(1,x)NoYesNoYesNo
All Read / One WriteN/AN/AN/AN/AN/AN/A
All Read / All Write(1,x)YesYesYesYesYes

For files defined to multiple regions without the use of an FOR (file owning region):

Access RequiredVSAM ShareoptionsFOA AddFOA BrowseFOA DeleteFOA ReadFOA Update
All Read / No Write(1,x)NoYesNoYesNo
All Read / One Write (2,x)Yes in one region, No in all other regionsYesYes in one region, No in all other regionsYesYes in one region, No in all other regions
All Read/All Write(2,x) + RLSYesYesYesYesYes

For files defined to multiple regions using an FOR (file owning region):

Access RequiredVSAM ShareoptionsFOA AddFOA BrowseFOA DeleteFOA ReadFOA Update
All Read / No Write(1,x)NoYesNoYesNo
All Read / One Write(1,x)Yes in the FOR region, No in all other regionsYesYes in the FOR region, No in all other regionsYesYes in the FOR region, No in all other regions
All Read/All Write(1,x)YesYesYesYesYes

In addition, the following applies to defining HostBridge files in an FOR:

  • The files must be defined as local in the FOR region
  • The files must be defined as remote in the non-FOR regions that access the files
  • Use of a CICS Table to define the files is recommended to obtain the highest performance

In all cases, properly sized LSRPools will improve performance.

When you install HostBridge, the default SHAREOPTIONS value for all files is (1,x) and files will be allocated on that basis.  If your configuration requires SHAREOPTIONS(2,x), the files will need to be ALTERed or reallocated.  

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