Gen Host Encyclopedia Disaster Recovery (DR) and data replication

Products

• Gen - Host Encyclopedia
• Gen

Issue/Introduction

For 2 sites with CA Gen Host Encyclopedia (HE) installed, one Active/Primary and one Disaster Recovery (DR).

1. What HE tables need to be replicated from the Active HE DB2 database to the DR HE DB2 database to ensure all operations executed on the Active site like check-in, checkout etc are also reflected on the DR site?

2. It is planned to make the DR HE tables read-only, but also want to be able to run code generation there. Will read-only access cause code generation a problem?

Environment

Release : 8.6

Component : CA Gen Host Encyclopedia

Resolution

1. To enable all Active HE operations to be visible on the DR HE and ensure 100% data integrity requires replication of all the HE Data tables from the Active HE DB2 database to the DR HE DB2 database. If the Active goes down and DR is required to become the new Active, the data will then be consistent across all the Data tables.
This documentation page reference covers those tables: CA Gen 8.6 > Encyclopedia > Host Encyclopedia > Host Encyclopedia > Reference > HE DATA TABLES
The above advice assumes the DR HE has already been installed and the maintenance/PTF level on Active/DR is the same. In that way, the Schema tables will match and there should be no need to replicate those tables.
If future PTFs are installed on the Active then the same should be installed on the DR, in case any Schema tables are changed by those PTFs.

2. Code generation will update some HE Data tables, so if it is planned to have all DR Data tables as read-only that will not allow code generation to take place.
These tables require write access for code generation:
 - DPRP (Generation Date and Generation Time are properties)
 - DOBJ (some scenarios may cause new objects to be created during the generation process)
 - DHLOG and DHOBJ history tables. If object history is disabled then the DHOBJ table should not be updated.
Enabling write access on those 4 tables to allow generation could cause potential replication issues. If the DB2 replication from Active to DR is "Active-Passive" (one way) and is only taking incremental table changes across then when the next replication occurs that will potentially cause a data conflict with object ids because of the previous generation updates to those 4 tables in DR. So the only solution may be to completely replace those 4 tables on each replication. In that way, any history in DR of generations done there would be lost, but that may not be significant if the objective is just to be able to generate code in DR "on the fly".

Additional Information

NOTES:
1. It is not possible to perform checkout/checkin on the DR HE without ALL Data tables having write access.
2. If requiring full functionality on both Active and DR HEs at the same time perhaps "Active-Active" replication should be considered.