Learning notes from the learning journey: Installing and Administering SAP HANA to take the Certification "SAP Certified Associate - Database Administrator - SAP HANA".
- Starting and Stopping SAP HANA:
To start or stop the SAP HANA Database it is possible to split the whole system, stop tenant(s), single instance, or Services.
In the first case, you can use the Cockpit (adm, Cockpit User, Database User) and sapcontrol (root, adm).
In the second case, Cockpit or SQL console or hdbsql (adm, Database user).
The third case, HDB (adm) and SAPControl.
And finally, the services, Cockpit and SQL console or hdbsql.
The SAPControl, you must log on to the SAP System host as a user or as root permissions. Avoid using the SYSTEM user for day-to-day activities.
It's important to highlight when working with Individual Tenants, the cockpit supports their start/stop, but the studio does not support it.
When dealing with SAP HANA Database Services, it's possible to stop: Name Server, Preprocessor, Web dispatcher, Compile Server, Index Server, XS Engine. In all the cases, either database services or services of a tenant database are necessary SYSTEM PRIVILEGES.
- Changing Database Configuration Parameters:
Display and change parameters are used Database Configuration App in Cockpit. To make changes, is necessary to have System Privileges.
There is a hierarchy of parameter values, which SAP stores in configuration files on the op. System Level:
1) DEFAULT
2) SYSTEM
3) DATABASE
4) HOST
- Describing Further Configuration Functions:
RESTRICTED FEATURES: Some features are not required in environments. It's possible to desirable them if you have system privileges, INIFILE ADMIN.
BLOCKLISTED PARAMETERS: Avoid tenant database administrators to change system properties. Also, need the system privileges INIFILE ADMIN. The changes can be done in the multidb.ini, once you have the System Privilege.
PARAMETERS: once a few parameters, the system might need to restart and some other analysis. To access this, there are two views in SAP database system:
1) CONFIGURATION_PARAMETER_PROPERTIES: metadata and properties of public config.
2) M_CONFIGURATION_PARAMETER_VALUES: landscape service values.
- Describing the Concept of Delta Merge:
DELTA MERGE PROCESS: It's an operation to move changes collected in the delta storage to the read-optimized main storage (In-Memory). This optimizes compression and write performance.
The process consists of three stages:
1) Before the write operations are done in Delta 1 and read on Main 1 and Delta 1.
2) During merge: The Main 1 and Delta 1 are combined in Main 2, meanwhile the write operation happens in Delta 2. The reading is done in all Tables beside Main 2.
3) After merge: The Main 1 and Delta 1 are deleted. Main 2 is compressed to the memory and Delta 2 takes the place of Delta 1.
PERFORM DELTA MERGE OP: Cockpit -> Current Table Distribution app. -> View Current Table Distribution -> Table Distribution card
DELTA MERGE EXPENSES: Creates disk input/output load, main storage is in-memory.
MERGE MOTIVATIONS FROM DELTA STORAGE TO MAIN STORAGE:
1) Automatic System Process:
a) Auto: mergedog system process is on (AUTO_MERGE_ON).
b) Critical Merge: The system initiates a critical merge automatically when a certain threshold is passed.
2) User/App task:
a) Hard/Forced: This can be triggered by SQL when the system is heavy and small tables need to be loaded.
b) Smart Merge: Merge is considered only if the criteria are met.
DELTA MERGE FEATURES: They are executed on table level.The operation is decoupled from the execution of the transaction that performs the changes, it happens asynchronously at a later point in time.
- Working with TRACES:
Cockpit -> View Trace and diagnostic files // Database Explore -> SYSTEM
To configure traces must have system privileges. For kernel profiles, and must have SAP_INTERNAL_HANA_SUPPORT standard role.
TYPES OF TRACES:
1) Database traces: they are always active (the only active by default). Tenant Database inherits the database trace level configured in the system database (default).
2) User-specific and End-to-end database
3) SQL Trace: Collected all the SQL Statements executed on the index server or name server.
4) Performance trace: Record performance indicator for individual query processing steps in the database kernel.
5) Expensive Statement trace: SQL statements whose execution time exceeds a configured threshold.
Access: Cockpit -> Trace Config. -> Expensive Statements Trace -> Database Explore -> M_EXPENSIVE_STATEMENTS (view)
6) Kernel Profiler
7) Plan Trace: collect SQL queries and execution plans in a time frame. It's checked in the SELECT statement with Plan Trace.
SQL TRACE ANALYZER: This is a Python tool used to analyze the SQL trace output from SAP.
MANAGE FULL SYSTEM INFORMATION DUMPS APP: collects all the import diagnosis information in ZIP file (support trace analysis).
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