Access to the product database is controlled with the help of the SYNC file. Only one subsystem (either started task or batch job) has direct access to the product database at a given time. If other subsystems access the product database, they do so indirectly, namely via the subsystem which has control over the database.
The subsystem which has direct access to the product database is called the master. When the STC or batch job is started, an entry is made in the SYNC file of the product database. This entry, which includes the SSID of the STC or batch job, gives the subsystem exclusive control over the database. When the STC is stopped or the batch job has terminated, the entry in the SYNC file is removed.
An entry in the SYNC file prevents any other subsystem from gaining direct access to the database. If other subsystems access the product database while it is under control of a master subsystem, they do so indirectly via the master subsystem. Subsystems which have only indirect access to a product database are called slaves.
Specify SIGNON=YES in the JCL of the batch job for indirect access to the product database (slave).
Specify SIGNON=NO in the JCL of the batch job for direct access to the product database (master).
The subsystem ID of the master subsystem must be specified in the LST parameter BQL_MASTER_SSID.
In case of a slave subsystem, the SSID and the BQL_MASTER_SSID are different.
In case of a master subsystem, the SSID and the BQL_MASTER_SSID are identical.
If an STC or batch job terminates abnormally, the entry in the SYNC file is not removed and other subsystems are prevented from gaining control over the product database. If you want to enable other subsystems to gain access to the product database, clear the SYNC file by one of the following methods:
An existing entry in the SYNC file prevents other subsystems from taking control over the database, but it does not prevent the same subsystem from regaining control. Subsystem-related information in the SYNC file is checked during restart. The entry in the SYNC file will be removed when the STC is stopped or the batch job terminates properly.
If an STC or batch job has terminated abnormally, another subsystem from the same sysplex (same GRS complex) is allowed to gain control over the database. A GRS enqueue safeguards against several subsystems taking control of the same database.
You can run job BnnCLSYN to clean the SYNC file (see "BnnCLSYN: Cleaning the SYNC file").