NAME

       pmempool-transform - Modify internal structure of a pool set.

SYNOPSIS

              pmempool transform [options] <poolset_file_src> <poolset_file_dst>

DESCRIPTION

       The  pmempool transform command modifies internal structure of a pool set defined by the poolset_file_src
       file, according to a structure described in the poolset_file_dst file.

       The following operations are supported:

       • adding replicas - one or more new replicas can be added and synchronized with  other  replicas  in  the
         pool set,

       • removing replicas - one or more replicas can be removed from the pool set ,

       • adding or removing pool set options.

       Only one of the above operations can be performed at a time.

       Currently adding and removing replicas are allowed only for pmemobj pools (see libpmemobj(7)).

       The poolset_file_src argument provides the source pool set to be changed.

       The poolset_file_dst argument points to the target pool set.

       When  adding  or deleting replicas, the two pool set files can differ only in the definitions of replicas
       which are to be added or deleted.  When adding or removing pool set options (see poolset(5)), the rest of
       both pool set files have to be of the same structure.  The operation of adding/removing a pool set option
       can be performed on a pool set with local replicas only.  To add/remove a pool set option to/from a  pool
       set  with  remote  replicas, one has to remove the remote replicas first, then add/remove the option, and
       finally recreate the remote replicas  having  added/removed  the  pool  set  option  to/from  the  remote
       replicas'  poolset files.  To add a replica it is necessary for its effective size to match or exceed the
       pool size.  Otherwise the whole operation fails and no changes are  applied.   If  none  of  the  poolset
       options  is  used, the effective size of a replica is the sum of sizes of all its part files decreased by
       4096 bytes per each part file.  The 4096 bytes of  each  part  file  is  utilized  for  storing  internal
       metadata of the pool part files.  If the option SINGLEHDR is used, the effective size of a replica is the
       sum of sizes of all its part files decreased once by 4096 bytes.   In  this  case  only  the  first  part
       contains  internal metadata.  If the option NOHDRS is used, the effective size of a replica is the sum of
       sizes of all its part files.  In this case none of the parts contains internal metadata.

   Available options:
       -d, --dry-run
              Enable dry run mode.  In this mode no changes  are  applied,  only  check  for  viability  of  the
              operation is performed.

       -v, --verbose
              Increase verbosity level.

       -h, --help
              Display help message and exit.

EXAMPLES

   Example 1.
       Let files /path/poolset_file_src and /path/poolset_file_dst have the following contents:

              PMEMPOOLSET
              20M /0/partfile1
              20M /0/partfile2
              25M /0/partfile3
              REPLICA
              40M /1/partfile1
              20M /1/partfile2

              PMEMPOOLSET
              20M /0/partfile1
              20M /0/partfile2
              25M /0/partfile3
              REPLICA
              40M /1/partfile1
              20M /1/partfile2
              REPLICA
              50M /2/partfile1
              20M /2/partfile2

       Then, the command

       pmempool transform /path/poolset_file_src /path/poolset_file_dst

       adds  a  replica  to  the pool set.  All other replicas remain unchanged and the size of the pool remains
       60M.

   Example 2.
       Let files /path/poolset_file_src and /path/poolset_file_dst have the following contents:

              PMEMPOOLSET
              20M /0/partfile1
              20M /0/partfile2
              25M /0/partfile3
              REPLICA
              40M /1/partfile1
              20M /1/partfile2

              PMEMPOOLSET
              20M /0/partfile1
              20M /0/partfile2
              25M /0/partfile3

       Then

       pmempool_transform /path/poolset_file_src /path/poolset_file_dst

       deletes the second replica from the pool set.  The first replica remains unchanged and the  size  of  the
       pool is still 60M.

SEE ALSO

       pmempool(1), libpmemblk(7), libpmemlog(7), libpmempool(7) and <https://pmem.io>