.. _3.6.3-1.1:

=================
|PSMDB| 3.6.3-1.1
=================

:Date: April 24, 2018
:Download: http://www.percona.com/downloads/percona-server-mongodb-3.6/
:Installation: :ref:`install`

|PSMDB| is an enhanced, open source, and highly-scalable database that is
a fully-compatible, drop-in replacement for MongoDB 3.6 Community Edition.
It supports MongoDB 3.6 protocols and drivers.

|PSMDB| extends Community Edition functionality by including the
:ref:`inmemory` storage engine, as well as several enterprise-grade features.
|PSMDB| requires no changes to MongoDB applications or code.

This release is based on `MongoDB 3.6.3
<https://docs.mongodb.com/manual/release-notes/3.6/#february-23-2018>`_
and provides the following additional changes:

* MongoRocks is deprecated in Percona Server for MongoDB 3.6 and it will be
  fully removed in the next major version of |PSMDB|. Feature compatibility
  version is set to 3.4 when using |PSMDB| 3.6 with MongoRocks, so 3.6
  features, such as retryable writes and causal consistency, cannot be used.
  Additionally, read concern majority may produce unreliable results.

* :jirabug:`PSMDB-191`: Fixed a bug in :ref:`mongorocks` engine initialization
  code which caused wrong initialization of ``_maxPrefix`` value. This could
  lead to reuse of dropped prefix and to accidental removal of data from the
  collection using reused prefix.

  In some specific conditions data records could disappear at arbitrary moment
  of time from the collections or indexes created after server restart.

  This could happen as the result of the following sequence of events:
   1. User deletes one or more indexes or collections. These should be the ones
      using maximum existing prefixes values.
   2. User shuts down the server before :ref:`mongorocks` compaction thread
      executes compactions of deleted ranges.
   3. User restarts the server and creates new collections. Due to the bug
      those new collections and their indexes may get the same prefix
      values which were deleted and not yet compacted. User inserts some
      data into the new collections.
   4. After the server restart :ref:`mongorocks` compaction thread continues
      executing compactions of the deleted ranges and this process may
      eventually delete data from the collections sharing prefixes with
      deleted ranges.

* :jirabug:`PSMDB-178`: RocksSnapshotManager was reworked to match the new model
  of interaction between MongoDB and storage engine's snapshot manager.