To understand the concept of the load and replication procedures in more detail, the following section explain s in more detail the purpose the major jobs involved in the replication process.
1. Master Job (Monitoring Job)
Naming Convention: IUUC_MONITOR_<MT_ID>
Every 5 seconds, the monitoring job checks in the SAP HANA system whether there are new tasks and, if so, triggers the master control jobs. It also deletes the processed entries (tasks) from table RS_ORDER and writes statistics entries into table RS_STATUS (in the relevant schema in the SAP HANA syst em).
Note: Every day at midnight, the monitoring job and related data load jobs - but not the migration object definition or access plan calculation jobs – are automatically stopped and restarted immediately. This action has no negative impact on the ongoi ng data load and replication, it will simple resume immediately.
However, this procedure allows several activities on specific SAP LT Replication Server control tables that avoids potential long- term performance issues with the SAP LT Replication Server and simplifies a lot of log and job- related troubleshooting activities, for example by providing the option to filter by date in transaction SM37.
2. Master Controller Job
Naming Convention: IUUC_REPLIC_CNTR_<MT_ID>
This job is scheduled on demand and is responsible for:
• Creating database triggers and logging table in the source system
• Creating synonyms
• Writing new entries in admin tables in SLT server when a new table is loaded/replicated
3. Data Load Job
Naming Convention: DTL_MT_DATA_LOAD_<MT_ID>_<2digits >
This job should always be active. If the job does not complete successfully, the master controller job restarts it.
This job is responsible for:
• Loading data (load)
• Replicating data (replication)
• Changing status flag for entries in control tables in the SAP LT Replication Server
4. Migration Object Definition Job
Naming Convention: IUUC_DEF_MIG_OBJ_<2digits>
This job defines the migration object of a specific table (that you choose to load/replicate), which is the fundamental object for LT replication. The migration object definition should normally be quite fast for all tables.
5. Access Plan Calculation Job
Naming Convention: ACC_PLAN_CALC_<MT_ID>_<2digits>
This job calculates the access plan of a specific table (that you choose to load/replicate), and the ac cess plan is used for data load or replication. The access plan is also a
fundamental object for the replication. For a normal sized table, access plan calculation should finish quite quickly (less than 1 minute) while large tables might take up to several hours to finish.
What is the relationship between the number of data transfer jobs in the configuration settings and the available BGD work processes?
Each job occupies 1 BGD work process in the SAP LT Replication Server. For each configuration, the para meter Data Transfer Jobs restricts the maximum number of data load job for each mass transfer ID (MT_ID).
In total, a mass transfer ID (MT_ID) requires at least 4 background jobs to be available:
- One monitoring job (master job)
- One master controller job
- At least one data load job
- One additional job either for the migration objects definition, access plan calculation or to change configuration settings in the Configuration & Monitoring Dashboard.
Example: if you set the parameter “data transfer j obs” to 04 in a configuration “SCHEMA1”, a mass transfer ID 001 is assigned. As a result, the following jobs should be in the system:
• 1 Monitoring job: IUUC_MONITOR_SCHEMA1
• 1 Master controller job: IUUC_REPLIC_CNTR_001_0001
• At most 4 parallel jobs for MT_ID 001: DTL_MT_DATA_LOAD_001_01/~02/~03/~04