I have installed Appian 7.6 on my 64 windows 7 laptop with mysql 5.6.20 an

Can you post the whole error? it got truncated

Eduardo,
Here is complete error log.

14:37:15,466 INFO [stdout] (ServerService Thread Pool -- 88) at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
14:37:15,466 INFO [stdout] (ServerService Thread Pool -- 88) at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:147)
14:37:15,468 INFO [stdout] (ServerService Thread Pool -- 88) ... 64 more
14:37:15,468 INFO [stdout] (ServerService Thread Pool -- 88) Caused by: java.lang.IllegalStateException: [java:/jdbc/AppianPrimaryDS] Error during schema migration.
14:37:15,469 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.rdbms.hb.DataSourceManagerHbImpl.ensureSchema(DataSourceManagerHbImpl.java:612)
14:37:15,470 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.rdbms.hb.DataSourceManagerHbImpl.getEntityManagerFactory(DataSourceManagerHbImpl.jav
a:585)
14:37:15,471 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.common.config.AppianPersistenceSpringConfig$EntityManagerFactoryWrapper.getDelegate(
AppianPersistenceSpringConfig.java:176)
14:37:15,472 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.common.config.AppianPersistenceSpringConfig$EntityManagerFactoryWrapper.createEntity
Manager(AppianPersistenceSpringConfig.java:180)
14:37:15,473 INFO [stdout] (ServerService Thread Pool -- 88) at org.springframework.orm.jpa.JpaTransactionManager.createEntityManagerForTransaction(JpaTransactionM
anager.java:445)
14:37:15,475 INFO [stdout] (ServerService Thread Pool -- 88) at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:366)
14:37:15,476 INFO [stdout] (ServerService Thread Pool -- 88) ... 90 more
14:37:15,478 INFO [stdout] (ServerService Thread Pool -- 88) Caused by: java.lang.IllegalStateException: liquibase.exception.MigrationFailedException: Migration fail
ed for change set db-changelog-000009.xml::000009.3.11::appian:
14:37:15,479 INFO [stdout] (ServerService Thread Pool -- 88) Reason: liquibase.exception.DatabaseException: Error executing SQL ALTER TABLE `rm_entry_groups` AD
D PRIMARY KEY (`rm_entry_id`, `group_id`): Incorrect index name 'PRIMARY':
14:37:15,479 INFO [stdout] (ServerService Thread Pool -- 88) Caused By: Error executing SQL ALTER TABLE `rm_entry_groups` ADD PRIMARY KEY (`rm_entry_id`, `
group_id`): Incorrect index name 'PRIMARY':
14:37:15,481 INFO [stdout] (ServerService Thread Pool -- 88) Caused By: Incorrect index name 'PRIMARY'
14:37:15,482 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.rdbms.common.schema.SchemaMigrator.migrate(SchemaMigrator.java:145)
14:37:15,484 INFO [stdout] (ServerService Thread Pool -- 88) at com.appiancorp.rdbms.hb.DataSourceManagerHbImpl.ensureSchema(DataSourceManagerHbImpl.java:609)
14:37:15,484 INFO [stdout] (ServerService Thread Pool -- 88) ... 95 more
14:37:15,485 INFO [stdout] (ServerService Thread Pool -- 88) Caused by: liquibase.exception.MigrationFailedException: Migration failed for change set db-changelog-00
0009.xml::000009.3.11::appian:
14:37:15,486 INFO [stdout] (ServerService Thread Pool -- 88) Reason: liquibase.exception.DatabaseException: Error executing SQL ALTER TABLE `rm_entry_groups` AD
D PRIMARY KEY (`rm_entry_id`, `group_id`): Incorrect index name 'PRIMARY':
14:37:15,487 INFO [stdout] (ServerService Thread Pool -- 88) Caused By: Error executing SQL ALTER TABLE `rm_entry_groups` ADD PRIMARY KEY (`rm_entry_id`, `
group_id`): Incorrect index name 'PRIMARY':
14:37:15,488 INFO [stdout] (ServerService Thread Pool -- 88) Caused By: Incorrect index name 'PRIMARY'
14:37:15,490 INFO [stdout] (ServerService Thread Pool -- 88) at liquibase.changelog.ChangeSet.execute(ChangeSet.java:347)
14:37:15,491 INFO [stdout] (ServerService Thread Pool -- 88) at liquibase.changelog.visitor.UpdateVisitor.visit(UpdateVisitor.java:27)
14:37:15,492 INFO [stdout] (ServerService Thread Pool -- 8

I attached the log file.
Also some tables are being created.

server.txt