.\" Automatically generated by Pandoc 2.10.1
.\"
.TH "PMEMPOOL_SYNC" "3" "2020-10-28" "PMDK - pmempool API version 1.3" "PMDK Programmer's Manual"
.hy
.\" SPDX-License-Identifier: BSD-3-Clause
.\" Copyright 2017-2018, Intel Corporation
.SH NAME
.PP
\f[B]pmempool_sync\f[R](), \f[B]pmempool_transform\f[R]() - pool set
synchronization and transformation
.SH SYNOPSIS
.IP
.nf
\f[C]
#include <libpmempool.h>

int pmempool_sync(const char *poolset_file, 
    unsigned flags); (EXPERIMENTAL)
int pmempool_transform(const char *poolset_file_src,
    const char *poolset_file_dst, unsigned flags); (EXPERIMENTAL)
\f[R]
.fi
.SH DESCRIPTION
.PP
The \f[B]pmempool_sync\f[R]() function synchronizes data between
replicas within a pool set.
.PP
\f[B]pmempool_sync\f[R]() accepts two arguments:
.IP \[bu] 2
\f[I]poolset_file\f[R] - a path to a pool set file,
.IP \[bu] 2
\f[I]flags\f[R] - a combination of flags (ORed) which modify how
synchronization is performed.
.RS
.PP
NOTE: Only the pool set file used to create the pool should be used for
syncing the pool.
.RE
.RS
.PP
NOTE: The \f[B]pmempool_sync\f[R]() cannot do anything useful if there
are no replicas in the pool set.
In such case, it fails with an error.
.RE
.RS
.PP
NOTE: At the moment, replication is only supported for
\f[B]libpmemobj\f[R](7) pools, so \f[B]pmempool_sync\f[R]() cannot be
used with other pool types (\f[B]libpmemlog\f[R](7),
\f[B]libpmemblk\f[R](7)).
.RE
.PP
The following flags are available:
.IP \[bu] 2
\f[B]PMEMPOOL_SYNC_DRY_RUN\f[R] - do not apply changes, only check for
viability of synchronization.
.PP
\f[B]pmempool_sync\f[R]() checks that the metadata of all replicas in a
pool set is consistent, i.e.\ all parts are healthy, and if any of them
is not, the corrupted or missing parts are recreated and filled with
data from one of the healthy replicas.
.PP
If a pool set has the option \f[I]SINGLEHDR\f[R] (see
\f[B]poolset\f[R](5)), the internal metadata of each replica is limited
to the beginning of the first part in the replica.
If the option \f[I]NOHDRS\f[R] is used, replicas contain no internal
metadata.
In both cases, only the missing parts or the ones which cannot be opened
are recreated with the \f[B]pmempool_sync\f[R]() function.
.PP
\f[B]pmempool_transform\f[R]() modifies the internal structure of a pool
set.
It supports the following operations:
.IP \[bu] 2
adding one or more replicas,
.IP \[bu] 2
removing one or more replicas ,
.IP \[bu] 2
adding or removing pool set options.
.PP
Only one of the above operations can be performed at a time.
.PP
\f[B]pmempool_transform\f[R]() accepts three arguments:
.IP \[bu] 2
\f[I]poolset_file_src\f[R] - pathname of the pool \f[I]set\f[R] file for
the source pool set to be changed,
.IP \[bu] 2
\f[I]poolset_file_dst\f[R] - pathname of the pool \f[I]set\f[R] file
that defines the new structure of the pool set,
.IP \[bu] 2
\f[I]flags\f[R] - a combination of flags (ORed) which modify how
synchronization is performed.
.PP
The following flags are available:
.IP \[bu] 2
\f[B]PMEMPOOL_TRANSFORM_DRY_RUN\f[R] - do not apply changes, only check
for viability of transformation.
.PP
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 \f[B]poolset\f[R](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\[cq] 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 pool set 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 \f[I]SINGLEHDR\f[R] 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 \f[I]NOHDRS\f[R] 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.
.RS
.PP
NOTE: At the moment, \f[I]transform\f[R] operation is only supported for
\f[B]libpmemobj\f[R](7) pools, so \f[B]pmempool_transform\f[R]() cannot
be used with other pool types (\f[B]libpmemlog\f[R](7),
\f[B]libpmemblk\f[R](7)).
.RE
.SH RETURN VALUE
.PP
\f[B]pmempool_sync\f[R]() and \f[B]pmempool_transform\f[R]() return 0 on
success.
Otherwise, they return -1 and set \f[I]errno\f[R] appropriately.
.SH ERRORS
.PP
\f[B]EINVAL\f[R] Invalid format of the input/output pool set file.
.PP
\f[B]EINVAL\f[R] Unsupported \f[I]flags\f[R] value.
.PP
\f[B]EINVAL\f[R] There is only master replica defined in the input pool
set passed to \f[B]pmempool_sync\f[R]().
.PP
\f[B]EINVAL\f[R] The source pool set passed to
\f[B]pmempool_transform\f[R]() is not a \f[B]libpmemobj\f[R] pool.
.PP
\f[B]EINVAL\f[R] The input and output pool sets passed to
\f[B]pmempool_transform\f[R]() are identical.
.PP
\f[B]EINVAL\f[R] Attempt to perform more than one transform operation at
a time.
.PP
\f[B]ENOTSUP\f[R] The pool set contains a remote replica, but remote
replication is not supported (\f[B]librpmem\f[R](7) is not available).
.SH NOTES
.PP
The \f[B]pmempool_sync\f[R]() API is experimental and it may change in
future versions of the library.
.PP
The \f[B]pmempool_transform\f[R]() API is experimental and it may change
in future versions of the library.
.SH SEE ALSO
.PP
\f[B]libpmemlog\f[R](7), \f[B]libpmemobj\f[R](7) and
\f[B]<https://pmem.io>\f[R]