SAP Hana - Data and Log Volume (File)

1 - About

Each volume contains one file (datavolume_0000.dat) in which data is organized into pages, ranging in size from 4KB to 16MB (page size class).

3 - Directory

During the installation process, the following default directories are created as the storage locations for data and log volumes:

  • /usr/sap/<SID>/SYS/global/hdb/data
  • usr/sap/<SID>/SYS/global/hdb/log

4 - Type

4.1 - Data

The data volume contains the data from the last completed savepoint.

4.2 - Log

The log volume contains all changes on the data volume since the last completed savepoint.

Each log volume contains the file logsegment_<partition_ID>_directory.dat and one or more log segment files (logsegment_<partition_ID>_<segment_number>.dat).

Currently only one log partition is supported for each service, so the default file names are:

  • logsegment_000_directory.dat
  • and logsegment_000_00000000.dat, logsegment_000_00000001.dat, logsegment_000_00000002.dat
  • and so on.

Log segment files are cyclically overwritten depending on the log mode. The log mode determines how logs are backed up. Log volumes only grow if there are no more segment files available for overwriting.

5 - Service

The services that persist data and therefore have volumes are the following:

  • nameserver Only the nameserver service on the active master host persists data. Slave namesever hosts communicate with the master, but do not persist data.
  • indexserver. The indexserver service on all hosts except standby hosts persists data.
  • xsengine (if running). The xsengine service persists data on any host on which it is running.

6 - Management

6.1 - Reclaim log

Log segment files that are available for overwriting have been backed up and are not required for a database restart. If necessary you can remove these files to free up space in your file system by executing the SQL statement ALTER SYSTEM RECLAIM LOG.

6.2 - Data Dictionary

7 - Configuration

7.1 - Default directories

The default directories are defined in the parameters basepath_datavolumes and basepath_logvolmes in the persistence section of the global.ini file.

8 - Documentation / Reference


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