Root based CDB and CfgSnapshot Snapshots

Snapshots
Naming convention

Snapshots

A snapshot is taken from a production federation. Currently the MASTER is used for CDB snapshots and IR2 is used for CfgDB. Once the MySQL/root implementation will become available it will be used.

The conditions that are extracted depend of the type of the snapshot (e.g.: cond18boot) and the subset of conditions needed (e.g.: betamini, full).

A snapshot could be self consistent or incremental. A self consistent snapshot contains all the needed data. An incremental snapshot however, contains only data that changed compared to a previous snapshot and it has to be merged with the previous snapshot.

For the the configuration database (CfgDb) a snapshot consists of only one file. A conditions database (CDB) snapshot consists of many file and therefore a bootfile is created that acts as a file catalog.

Naming Conventions

The following naming conventions for the conditions and configuration root files are used.

Domain	Naming Convention
Configurations	/store/cfg/<YYYY>/<MM>/CfgDB-<DateTime>.root Example: /store/cfg/2006/01/CfgDB-20060118T185125.root
Conditions	/store/cdb/<Type>/<subSet>/<YYYY>/<MM>/<DateTime>/CDB-<DateTime>-<components>.root Example: /store/cdb/cond18boot/betamini/2006/01/20060119T134600/Cdb-20060119T134600-cdb_o257_c0_p33_i0.root
Ambient	> ....../Amb-<components>.root

where

<YYYY>: Year the snapshot was taken in 4 digits (e.g.: 2006)
<MM>: Month the snapshot was taken in 2 digits (e.g.: 03)
<DateTime>: Date and time the snapshot was taken. UTC time is used. The date and time are separated by a capital T (as suggested by ISO 8601). <YYYYMMDD>T<HHMMSS> for example 20060118T183012
<Type>: The Type of a conditions snapshot would be cond18boot,
<subSet>: Describes which conditions are extracted. For example, if subSet=full all conditions are extracted. With subSet=betaMini only those conditions needed for a betaMini analysis jobs are extracted which makes the snapshot smaller compared to a full snapshot (but it can only be used for betaMini jobs). Another possibility would be a subset that is only valid for a certain time period. For example one could take an SP8 (type) snapshot but it contains only conditions for a certain time range (subSet).

Snapshot Types
Type	Comment
cond18boot	Cond18boot like conditions

Snapshot subsets
subSet	Comment
full	contains all conditions for a particular snapshot type
betaMini	only conditions needed by BetaMini analysis jobs

Incremental Snapshot

An incremental snapshot is a snapshot that contains only those root files that changed compared to a previous snapshot. It is not that it only contains new conditions values.

Lets assume a snapshot is taken that contains three root files (meta data files are ignored).

Snapshot 1:
   183689 Jan 19 13:48 Cdb_20060119T134600_o256_c2_i1.root
   214296 Jan 19 13:48 Cdb_20060119T134600_o256_c2_i0.root
   401191 Jan 19 13:48 Cdb_20060119T134600_o0_c0_p21_i0.root

A few days later a new snapshot is taken. However in the mean time some conditions changed and therefore the o256_c2_i1.root will be different.

Snapshot 2:
   234599 Jan 26 11:23 Cdb_20060126T112200_o256_c2_i1.root
   214296 Jan 26 11:23 Cdb_20060126T112200_o256_c2_i0.root
   401191 Jan 26 11:24 Cdb_20060126T112200_o0_c0_p21_i0.root

The two files _o256_c2_i0.root and _o0_c0_p21_i0.root are identical but o256_c2_i1.root is larger as it contains more conditions. Therefore the incremental snapshot consists only of the file

Incremental Snapshot:
   234599 Jan 26 11:23 Cdb_20060126T112200_o256_c2_i1.root

Making a snapshot accessible for clients

After a snapshot has been imported to a local site and the files are accessible either through the local file system or Xrootd and few more steps are needed that allows a client to resolve a generic root file name to a specific root file in the snapshot. The document Import CfgDB snapshot describes what has to be done.

Last modified: Thu Aug 31 12:26:18 PDT 2006