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SAP SQL Anywhere, on-demand edition 1.0 SP 6 » Tenant databases » Synchronization and replication support

Restrictions for running MobiLink and SQL Remote in the cloud

There are several restrictions when running MobiLink and SQL Remote in the cloud.

Settings and system requirements for synchronization and replication in the cloud

If you are using a tenant database as a remote database for MobiLink or as a consolidated or remote database for replication using SQL Remote, then the cloud must be set to allow database servers to list files in active transaction log directories and read and delete offline transaction log files from the active log directory, because dbmlsync and dbremote need to access offline transaction log files of databases in the cloud.

To set the cloud to allow database servers to list files in active transaction log directories and read and delete offline transaction log files from the active log directory, run the AlterCloud task and set the secure_feature_list with the following properties:

all,-sp_list_directory,-read_file,-sp_delete_file
Note All the properties must be specified on a single line.

To run synchronization and replication in the cloud, your system must meet the following requirements:

  • The cloud must not have any SQL Anywhere version 12 servers.
  • All SQL Anywhere servers in the cloud must be version 16.0.0.2001 later.
  • Your cloud infrastructure must be SP 6 or later.
MobiLink consolidated tenant database

Synchronizing with a MobiLink consolidated tenant database can be accomplished with the following considerations.

  • Installation

    When you are using a MobiLink consolidated database as a tenant database, MobiLink can be installed on a computer that also hosts cloud servers or on a computer that is independent of the cloud, provided it has network connectivity to the cloud.

  • Mirroring

    If you are using a mirrored consolidated database, then the connection string must contain NODE=PRIMARY (which is the default), when applying syncsa.sql and also when launching mlsrv17.

MobiLink remote tenant database

You can synchronize a MobiLink remote tenant database within a cloud. However, there are a number of considerations to be aware of when setting up this synchronization scenario.

  • Installation

    You can install dbmlsync in or out of the cloud, as long as dbmlsync can access the cloud.

  • Database setup

    A MobiLink remote database can be set up before adding it to the cloud or a database that is already in a cloud can be set up for synchronization as a remote database.

    If the database is already set up for synchronization as a remote database before it is added to the cloud, then you must add all the transaction log files to the cloud, including the online log and the offline logs.

  • Transaction log files

    With transaction log-based uploads, dbmlsync must either be able to directly access the offline transaction log files or retrieve offline transaction log files through its database server running in the cloud.

    If it is not feasible to directly access offline transaction logs, then you can run dbmlsync from any computer that can connect to the databases in the cloud. In this case, dbmlsync retrieves offline transaction logs through its database server in the cloud if offline transaction logs are needed, but the given offline log directory from the dbmlsync command line cannot be opened or does not contains an offline transaction log file.

    With script-based uploads, dbmlsync can be run on any computer that contains a dbmlsync installation, and no transaction log is required.

  • Mirroring

    When you are using a mirrored remote, the connection string must contain NODE=PRIMARY (which is the default), both when creating publications and subscriptions, and when launching dbmlsync.

  • Moving databases

    When you are moving a remote database to a different cloud server (on the same host) or to a different host:

    • Stop the database before moving. If it is still running, log files will be lost after moving.

    • Restart dbmlsync once you move the remote database.

SQL Remote consolidated tenant database

You can use a SQL Remote consolidated database as a tenant database with the following considerations and restrictions.

  • Installation

    SQL Remote can be either in the cloud or outside it, but it must be able to access the cloud.

  • Database setup

    The SQL Remote consolidated database can be set up before adding it to the cloud or the database can be set up for replication as a consolidated database within the cloud. You cannot use this database as a message server if you are using the HTTP or HTTPS message type for replication because the messages must be readable and writable by dbremote through the file system.

    If the database is already set up for replication before it is added to the cloud, then you must add all the transaction log files, including the online logs and the offline logs, to the cloud.

  • Transaction log files

    If you are using bi-directional replication or send mode (-s), then dbremote must be able to either directly access offline transaction log files or retrieve offline transaction log files through the database server running in the cloud.

    If it is not feasible to directly access offline transaction logs, then you can run dbremote from any computer that can connect to the databases in the cloud. In this case, dbremote retrieves offline transaction logs through its database server in the cloud if offline transaction logs are needed, but the given offline log directory from the dbremote command line cannot be opened or contains no offline transaction log file. All offline transaction log files must be in the active transaction log directory of the database in the cloud and the cloud security features must conform to the required cloud settings.

    If you are using receive-only mode (-r), then no access to transaction logs is required.

  • Mirroring

    When you are using a mirrored consolidated database, the connection string must contain NODE=PRIMARY, which is the default.

  • Moving databases

    When you are moving a consolidated database to a different cloud server (on the same host) or to a different host:

    • All of the restrictions and conditions listed above apply.

    • Current replications fail and new replications succeed once the new primary is available.

    • Restart dbremote once you move the consolidated database.

SQL Remote remote tenant database

You can use a SQL Remote remote database as a tenant database with the following considerations and restrictions.

  • Installation

    Install SQL Remote in a location that can access the cloud.

  • Database setup

    The SQL Remote remote database can be set up before adding it to the cloud, or the database can be set up for replication as a remote database within the cloud by using the Extraction utility (dbxtract) when the database is already in the cloud. You may need to run dbxtract with the -ac and -xx command line options if you need to extract the schema as well as the data of replicated tables from the consolidated database.

    If the database is already set up for replication before it is added to the cloud, then you must add all the transaction log files, including the online logs and the offline logs, to the cloud.

  • Transaction log files

    If you are using bi-directional replication (the default) or send mode (-s), then dbremote must be able to either directly access offline transaction log files or retrieve offline transaction log files through the database server running in the cloud.

    If it is not feasible to directly access offline transaction logs, then you can run dbremote from any computer that can connect to the databases in the cloud. In this case, dbremote retrieves offline transaction logs through its database server in the cloud if offline transaction logs are needed but the given offline log directory from the dbremote command line cannot be opened or contains no offline transaction log file. All offline transaction log files must be in the active transaction log directory of the database in the cloud and the cloud security features must conform to the required cloud settings.

    If you are using receive-only mode (-r), then no access to transaction logs is required.

  • Mirroring

    When you are using a mirrored remote database, the connection string must contain NODE=PRIMARY (which is the default), when applying the reload.sql file and also when invoking dbremote.

  • Moving databases

    When you are moving a remote database to a different cloud server on the same host, or to a different host:

    • All of the same restrictions and conditions listed above apply.

    • Restart dbremote once you move the remote database.

Note Replication of a SQL Remote HTTP message server tenant database is not supported.
Upgrade restrictions

If you have installed the dbmlsync and dbremote utilities to run with the cloud, then you must reinstall the files on each host that runs a copy of the primary database copy and mirror database copy for the tenant databases involved in synchronization each time you upgrade the cloud infrastructure.