Command Line Arguments

The general form of the Comdb2 command line is

      comdb2 [--lrl LRLFILE] [--recovertotime EPOCH]
             [--recovertolsn FILE:OFFSET]
             [--fullrecovery] NAME
  
      comdb2 --create [--lrl LRLFILE] [--dir PATH] NAME
  
       --lrl                      specify alternate lrl file
       --fullrecovery             runs full recovery after a hot copy
       --recovertolsn             recovers database to file:offset
       --recovertotime            recovers database to epochtime
       --create                   creates a new database
       --dir                      specify path to database directory
  
       NAME                       database name
       LRLFILE                    lrl configuration file
       FILE                       ID of a database file
       OFFSET                     offset within FILE
       EPOCH                      time in seconds since 1970
       PATH                       path to database directory

Options are optional

Specifying the database directory

Using –lrl

By default, the database will look in the standard install path for a database with the given name. That defaults to ${COMDB2_ROOT}/var/cdb2/${dbname}. If that directory contains a ${dbname}.lrl file, the database will use it to determine its startup options. The database will also look in the current directory for a ${dbname}.lrl

The database can be directed to use a specific lrl file with the -lrl option. It takes a path to the lrl file as an argument.

Using –dir

If the lrl file isn’t found, and isn’t specified, the database will try to start with default options, from the default location. That’s still ${COMDB2_ROOT}/var/cdb2/${dbname} followed by the current directory. If these locations contain a database, it’ll try to start with default options. The directory can be specified with the -dir option. It takes a path to the database directory as an argument.

Creating a new database

Using –create

A new database must be created with the --create option. If a directory is specified with --dir, the database will be created there. If it isn’t, Comdb2 will use the value of a COMDB2_DB_DIR environment variable, if it’s set. Otherwise, it’ll try to create the database in the default directory ${COMDB2_ROOT}/var/cdb2/${dbname}.

If an lrl file is specified with the --lrl option, the database will apply options it. Note that some options can only be specified at creation time. If no lrl file is specified, the database will create an ${dbname}.lrl file in the database directory with the default options. Running comdb2 ${dbname} will start this database (see Specifying the database directory).

The database has some options to guide recovery at startup time.

–fullrecovery

Attempts to recover from the earliest available checkpoint. Recovery normally starts at the latest checkpoint.

–recovertotime

Takes an integer epoch time as an argument. Unrolls all transactions that started later than this timestamps, even if they committed. This is useful for unrolling a database to a state as of a given timestamp.

–recovertolsn

Takes an LSN in a file:offset format. Unrolls all transactions that haven’t committed as of that LSN.